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	$63.69	4.215%	$66.3745	$66.37	$66.35	$66.40
Purchase #2	$240.29	9.822%	$263.8913	$263.89	$263.90	$263.90
Purchase #3	$54.74	5.109%	$57.5367	$57.54	$57.55	$57.50
Purchase #4	$186.91	4.175%	$194.7135	$194.71	$194.70	$194.70
Purchase #5	$125.41	7.792%	$135.1819	$135.18	$135.20	$135.20
Purchase #6	$170.48	3.156%	$175.8603	$175.86	$175.85	$175.90
Purchase #7	$100.26	10.826%	$111.1141	$111.11	$111.10	$111.10
7 purchase totals =	$941.78		$1,004.6723	$1,004.66	$1,004.65	$1,004.70