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	$99.97	11.736%	$111.7025	$111.70	$111.70	$111.70
Purchase #2	$135.44	3.472%	$140.1425	$140.14	$140.15	$140.10
Purchase #3	$134.65	7.365%	$144.567	$144.57	$144.55	$144.60
Purchase #4	$165.73	13.639%	$188.3339	$188.33	$188.35	$188.30
Purchase #5	$216.94	3.756%	$225.0883	$225.09	$225.10	$225.10
Purchase #6	$167.73	10.670%	$185.6268	$185.63	$185.65	$185.60
Purchase #7	$124.52	9.739%	$136.647	$136.65	$136.65	$136.60
7 purchase totals =	$1,044.98		$1,132.1080	$1,132.11	$1,132.15	$1,132.00