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	$64.39	12.260%	$72.2842	$72.28	$72.30	$72.30
Purchase #2	$204.96	9.434%	$224.2959	$224.30	$224.30	$224.30
Purchase #3	$49.96	4.799%	$52.3576	$52.36	$52.35	$52.40
Purchase #4	$64.93	3.804%	$67.3999	$67.40	$67.40	$67.40
Purchase #5	$99.61	13.834%	$113.39	$113.39	$113.40	$113.40
Purchase #6	$236.50	3.231%	$244.1413	$244.14	$244.15	$244.10
Purchase #7	$156.25	3.294%	$161.3969	$161.40	$161.40	$161.40
7 purchase totals =	$876.60		$935.2658	$935.27	$935.30	$935.30