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	$221.36	11.661%	$247.1728	$247.17	$247.15	$247.20
Purchase #2	$148.46	7.442%	$159.5084	$159.51	$159.50	$159.50
Purchase #3	$167.72	7.301%	$179.9652	$179.97	$179.95	$180.00
Purchase #4	$178.53	7.152%	$191.2985	$191.30	$191.30	$191.30
Purchase #5	$91.77	12.482%	$103.2247	$103.22	$103.20	$103.20
Purchase #6	$244.96	9.776%	$268.9073	$268.91	$268.90	$268.90
Purchase #7	$226.51	12.753%	$255.3968	$255.40	$255.40	$255.40
7 purchase totals =	$1,279.31		$1,405.4737	$1,405.48	$1,405.40	$1,405.50