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	$238.67	7.413%	$256.3626	$256.36	$256.35	$256.40
Purchase #2	$211.98	10.554%	$234.3524	$234.35	$234.35	$234.40
Purchase #3	$159.73	7.643%	$171.9382	$171.94	$171.95	$171.90
Purchase #4	$38.33	10.874%	$42.498	$42.50	$42.50	$42.50
Purchase #5	$17.51	5.107%	$18.4042	$18.40	$18.40	$18.40
Purchase #6	$206.55	11.519%	$230.3425	$230.34	$230.35	$230.30
Purchase #7	$93.60	7.136%	$100.2793	$100.28	$100.30	$100.30
7 purchase totals =	$966.37		$1,054.1772	$1,054.17	$1,054.20	$1,054.20