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	$140.53	4.121%	$146.3212	$146.32	$146.30	$146.30
Purchase #2	$57.95	3.324%	$59.8763	$59.88	$59.90	$59.90
Purchase #3	$196.41	13.413%	$222.7545	$222.75	$222.75	$222.80
Purchase #4	$112.30	10.753%	$124.3756	$124.38	$124.40	$124.40
Purchase #5	$97.73	9.512%	$107.0261	$107.03	$107.05	$107.00
Purchase #6	$138.62	6.145%	$147.1382	$147.14	$147.15	$147.10
Purchase #7	$244.40	6.292%	$259.7776	$259.78	$259.80	$259.80
7 purchase totals =	$987.94		$1,067.2695	$1,067.28	$1,067.35	$1,067.30