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	$48.33	10.131%	$53.2263	$53.23	$53.25	$53.20
Purchase #2	$53.46	10.340%	$58.9878	$58.99	$59.00	$59.00
Purchase #3	$229.27	10.524%	$253.3984	$253.40	$253.40	$253.40
Purchase #4	$244.76	11.453%	$272.7924	$272.79	$272.80	$272.80
Purchase #5	$122.59	11.677%	$136.9048	$136.90	$136.90	$136.90
Purchase #6	$158.40	12.456%	$178.1303	$178.13	$178.15	$178.10
Purchase #7	$54.62	13.701%	$62.1035	$62.10	$62.10	$62.10
7 purchase totals =	$911.43		$1,015.5435	$1,015.54	$1,015.60	$1,015.50