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	$196.98	13.252%	$223.0838	$223.08	$223.10	$223.10
Purchase #2	$140.76	12.444%	$158.2762	$158.28	$158.30	$158.30
Purchase #3	$79.45	11.279%	$88.4112	$88.41	$88.40	$88.40
Purchase #4	$139.65	4.649%	$146.1423	$146.14	$146.15	$146.10
Purchase #5	$63.61	5.680%	$67.223	$67.22	$67.20	$67.20
Purchase #6	$36.89	3.325%	$38.1166	$38.12	$38.10	$38.10
Purchase #7	$223.63	11.195%	$248.6654	$248.67	$248.65	$248.70
7 purchase totals =	$880.97		$969.9185	$969.92	$969.90	$969.90