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	$132.86	13.816%	$151.2159	$151.22	$151.20	$151.20
Purchase #2	$120.72	11.135%	$134.1622	$134.16	$134.15	$134.20
Purchase #3	$104.87	10.165%	$115.53	$115.53	$115.55	$115.50
Purchase #4	$187.97	6.470%	$200.1317	$200.13	$200.15	$200.10
Purchase #5	$200.66	4.468%	$209.6255	$209.63	$209.65	$209.60
Purchase #6	$148.54	5.272%	$156.371	$156.37	$156.35	$156.40
Purchase #7	$72.72	6.343%	$77.3326	$77.33	$77.35	$77.30
7 purchase totals =	$968.34		$1,044.3689	$1,044.37	$1,044.40	$1,044.30