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	$131.63	12.418%	$147.9758	$147.98	$148.00	$148.00
Purchase #2	$6.75	13.545%	$7.6643	$7.66	$7.65	$7.70
Purchase #3	$82.89	6.871%	$88.5854	$88.59	$88.60	$88.60
Purchase #4	$86.27	11.479%	$96.1729	$96.17	$96.15	$96.20
Purchase #5	$37.28	4.395%	$38.9185	$38.92	$38.90	$38.90
Purchase #6	$154.44	5.361%	$162.7195	$162.72	$162.70	$162.70
Purchase #7	$113.79	6.262%	$120.9155	$120.92	$120.90	$120.90
7 purchase totals =	$613.05		$662.9519	$662.96	$662.90	$663.00