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	$79.75	4.109%	$83.0269	$83.03	$83.05	$83.00
Purchase #2	$138.96	11.175%	$154.4888	$154.49	$154.50	$154.50
Purchase #3	$229.78	9.855%	$252.4248	$252.42	$252.40	$252.40
Purchase #4	$144.27	4.760%	$151.1373	$151.14	$151.15	$151.10
Purchase #5	$93.59	10.217%	$103.1521	$103.15	$103.15	$103.20
Purchase #6	$192.96	13.731%	$219.4553	$219.46	$219.45	$219.50
Purchase #7	$115.41	13.808%	$131.3458	$131.35	$131.35	$131.30
7 purchase totals =	$994.72		$1,095.0310	$1,095.04	$1,095.05	$1,095.00