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	$72.76	5.673%	$76.8877	$76.89	$76.90	$76.90
Purchase #2	$80.90	13.164%	$91.5497	$91.55	$91.55	$91.50
Purchase #3	$66.63	9.190%	$72.7533	$72.75	$72.75	$72.80
Purchase #4	$50.52	13.764%	$57.4736	$57.47	$57.45	$57.50
Purchase #5	$59.34	13.314%	$67.2405	$67.24	$67.25	$67.20
Purchase #6	$26.25	12.146%	$29.4383	$29.44	$29.45	$29.40
Purchase #7	$188.91	9.284%	$206.4484	$206.45	$206.45	$206.40
7 purchase totals =	$545.31		$601.7915	$601.79	$601.80	$601.70