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	$41.35	11.600%	$46.1466	$46.15	$46.15	$46.10
Purchase #2	$215.49	4.454%	$225.0879	$225.09	$225.10	$225.10
Purchase #3	$54.38	12.703%	$61.2879	$61.29	$61.30	$61.30
Purchase #4	$124.39	3.541%	$128.7946	$128.79	$128.80	$128.80
Purchase #5	$167.37	11.481%	$186.5857	$186.59	$186.60	$186.60
Purchase #6	$160.27	4.812%	$167.9822	$167.98	$168.00	$168.00
Purchase #7	$71.27	12.567%	$80.2265	$80.23	$80.25	$80.20
7 purchase totals =	$834.52		$896.1114	$896.12	$896.20	$896.10