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	$203.42	4.609%	$212.7956	$212.80	$212.80	$212.80
Purchase #2	$17.90	11.448%	$19.9492	$19.95	$19.95	$19.90
Purchase #3	$57.35	4.290%	$59.8103	$59.81	$59.80	$59.80
Purchase #4	$62.64	4.642%	$65.5477	$65.55	$65.55	$65.50
Purchase #5	$115.77	13.335%	$131.2079	$131.21	$131.20	$131.20
Purchase #6	$52.36	8.289%	$56.7001	$56.70	$56.70	$56.70
Purchase #7	$79.60	7.151%	$85.2922	$85.29	$85.30	$85.30
7 purchase totals =	$589.04		$631.3030	$631.31	$631.30	$631.20