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	$131.28	12.356%	$147.501	$147.50	$147.50	$147.50
Purchase #2	$207.36	7.568%	$223.053	$223.05	$223.05	$223.10
Purchase #3	$117.96	7.584%	$126.9061	$126.91	$126.90	$126.90
Purchase #4	$19.49	13.837%	$22.1868	$22.19	$22.20	$22.20
Purchase #5	$245.44	3.388%	$253.7555	$253.76	$253.75	$253.80
Purchase #6	$85.96	5.221%	$90.448	$90.45	$90.45	$90.40
Purchase #7	$131.89	5.589%	$139.2613	$139.26	$139.25	$139.30
7 purchase totals =	$939.38		$1,003.1117	$1,003.12	$1,003.10	$1,003.20