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	$169.59	10.213%	$186.9102	$186.91	$186.90	$186.90
Purchase #2	$149.65	5.163%	$157.3764	$157.38	$157.40	$157.40
Purchase #3	$85.80	10.858%	$95.1162	$95.12	$95.10	$95.10
Purchase #4	$209.60	10.487%	$231.5808	$231.58	$231.60	$231.60
Purchase #5	$92.87	6.822%	$99.2056	$99.21	$99.20	$99.20
Purchase #6	$151.39	6.182%	$160.7489	$160.75	$160.75	$160.70
Purchase #7	$114.58	13.571%	$130.1297	$130.13	$130.15	$130.10
7 purchase totals =	$973.48		$1,061.0678	$1,061.08	$1,061.10	$1,061.00