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	$191.60	4.552%	$200.3216	$200.32	$200.30	$200.30
Purchase #2	$108.44	7.603%	$116.6847	$116.68	$116.70	$116.70
Purchase #3	$110.89	11.698%	$123.8619	$123.86	$123.85	$123.90
Purchase #4	$187.51	10.254%	$206.7373	$206.74	$206.75	$206.70
Purchase #5	$42.52	10.345%	$46.9187	$46.92	$46.90	$46.90
Purchase #6	$65.89	10.303%	$72.6786	$72.68	$72.70	$72.70
Purchase #7	$67.47	12.804%	$76.1089	$76.11	$76.10	$76.10
7 purchase totals =	$774.32		$843.3117	$843.31	$843.30	$843.30