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	$223.79	6.612%	$238.587	$238.59	$238.60	$238.60
Purchase #2	$130.55	7.866%	$140.8191	$140.82	$140.80	$140.80
Purchase #3	$174.98	3.256%	$180.6773	$180.68	$180.70	$180.70
Purchase #4	$60.88	3.251%	$62.8592	$62.86	$62.85	$62.90
Purchase #5	$216.33	7.647%	$232.8728	$232.87	$232.85	$232.90
Purchase #6	$70.45	3.263%	$72.7488	$72.75	$72.75	$72.70
Purchase #7	$99.58	4.563%	$104.1238	$104.12	$104.10	$104.10
7 purchase totals =	$976.56		$1,032.6880	$1,032.69	$1,032.65	$1,032.70