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	$43.52	7.692%	$46.8676	$46.87	$46.85	$46.90
Purchase #2	$48.25	12.379%	$54.2229	$54.22	$54.20	$54.20
Purchase #3	$121.63	9.531%	$133.2226	$133.22	$133.20	$133.20
Purchase #4	$55.77	10.118%	$61.4128	$61.41	$61.40	$61.40
Purchase #5	$168.48	8.287%	$182.4419	$182.44	$182.45	$182.40
Purchase #6	$109.83	9.392%	$120.1452	$120.15	$120.15	$120.10
Purchase #7	$150.28	11.727%	$167.9033	$167.90	$167.90	$167.90
7 purchase totals =	$697.76		$766.2163	$766.21	$766.15	$766.10