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	$141.26	4.455%	$147.5531	$147.55	$147.55	$147.60
Purchase #2	$231.67	13.571%	$263.1099	$263.11	$263.10	$263.10
Purchase #3	$246.65	9.785%	$270.7847	$270.78	$270.80	$270.80
Purchase #4	$151.74	7.181%	$162.6364	$162.64	$162.65	$162.60
Purchase #5	$56.72	13.715%	$64.4991	$64.50	$64.50	$64.50
Purchase #6	$37.32	6.241%	$39.6491	$39.65	$39.65	$39.60
Purchase #7	$61.46	9.671%	$67.4038	$67.40	$67.40	$67.40
7 purchase totals =	$926.82		$1,015.6361	$1,015.63	$1,015.65	$1,015.60