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	$211.87	5.155%	$222.7919	$222.79	$222.80	$222.80
Purchase #2	$68.33	10.562%	$75.547	$75.55	$75.55	$75.50
Purchase #3	$106.98	4.399%	$111.6861	$111.69	$111.70	$111.70
Purchase #4	$31.85	7.108%	$34.1139	$34.11	$34.10	$34.10
Purchase #5	$48.42	6.247%	$51.4448	$51.44	$51.45	$51.40
Purchase #6	$135.29	12.417%	$152.089	$152.09	$152.10	$152.10
Purchase #7	$139.31	3.684%	$144.4422	$144.44	$144.45	$144.40
7 purchase totals =	$742.05		$792.1149	$792.11	$792.15	$792.00