Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.29	11.833%	$219.517	$219.52	$219.50	$219.50
Purchase #2	$84.71	12.821%	$95.5707	$95.57	$95.55	$95.60
Purchase #3	$209.56	6.713%	$223.6278	$223.63	$223.65	$223.60
Purchase #4	$162.30	10.495%	$179.3334	$179.33	$179.35	$179.30
Purchase #5	$214.41	11.207%	$238.4389	$238.44	$238.45	$238.40
Purchase #6	$93.96	13.329%	$106.4839	$106.48	$106.50	$106.50
Purchase #7	$242.32	5.769%	$256.2994	$256.30	$256.30	$256.30
7 purchase totals =	$1,203.55		$1,319.2711	$1,319.27	$1,319.30	$1,319.20