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	$209.40	5.203%	$220.2951	$220.30	$220.30	$220.30
Purchase #2	$236.58	12.325%	$265.7385	$265.74	$265.75	$265.70
Purchase #3	$37.55	5.367%	$39.5653	$39.57	$39.55	$39.60
Purchase #4	$52.69	4.789%	$55.2133	$55.21	$55.20	$55.20
Purchase #5	$134.68	10.294%	$148.544	$148.54	$148.55	$148.50
Purchase #6	$170.32	11.738%	$190.3122	$190.31	$190.30	$190.30
Purchase #7	$156.50	10.200%	$172.463	$172.46	$172.45	$172.50
7 purchase totals =	$997.72		$1,092.1314	$1,092.13	$1,092.10	$1,092.10