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	$149.28	3.385%	$154.3331	$154.33	$154.35	$154.30
Purchase #2	$48.80	11.814%	$54.5652	$54.57	$54.55	$54.60
Purchase #3	$40.56	3.535%	$41.9938	$41.99	$42.00	$42.00
Purchase #4	$185.27	3.713%	$192.1491	$192.15	$192.15	$192.10
Purchase #5	$111.74	5.193%	$117.5427	$117.54	$117.55	$117.50
Purchase #6	$136.85	11.642%	$152.7821	$152.78	$152.80	$152.80
Purchase #7	$237.84	12.872%	$268.4548	$268.45	$268.45	$268.50
7 purchase totals =	$910.34		$981.8208	$981.81	$981.85	$981.80