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	$58.36	5.144%	$61.362	$61.36	$61.35	$61.40
Purchase #2	$144.80	5.540%	$152.8219	$152.82	$152.80	$152.80
Purchase #3	$229.59	5.635%	$242.5274	$242.53	$242.55	$242.50
Purchase #4	$41.96	5.415%	$44.2321	$44.23	$44.25	$44.20
Purchase #5	$163.34	9.862%	$179.4486	$179.45	$179.45	$179.40
Purchase #6	$166.39	11.489%	$185.5065	$185.51	$185.50	$185.50
Purchase #7	$93.71	9.668%	$102.7699	$102.77	$102.75	$102.80
7 purchase totals =	$898.15		$968.6684	$968.67	$968.65	$968.60