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	$115.56	12.102%	$129.5451	$129.55	$129.55	$129.50
Purchase #2	$68.32	6.458%	$72.7321	$72.73	$72.75	$72.70
Purchase #3	$155.47	8.254%	$168.3025	$168.30	$168.30	$168.30
Purchase #4	$5.33	3.137%	$5.4972	$5.50	$5.50	$5.50
Purchase #5	$139.76	13.457%	$158.5675	$158.57	$158.55	$158.60
Purchase #6	$60.79	10.674%	$67.2787	$67.28	$67.30	$67.30
Purchase #7	$11.27	11.560%	$12.5728	$12.57	$12.55	$12.60
7 purchase totals =	$556.50		$614.4959	$614.50	$614.50	$614.50