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	$182.40	4.743%	$191.0512	$191.05	$191.05	$191.10
Purchase #2	$91.66	13.541%	$104.0717	$104.07	$104.05	$104.10
Purchase #3	$126.91	6.188%	$134.7632	$134.76	$134.75	$134.80
Purchase #4	$140.78	10.464%	$155.5112	$155.51	$155.50	$155.50
Purchase #5	$113.27	12.279%	$127.1784	$127.18	$127.20	$127.20
Purchase #6	$175.75	3.215%	$181.4004	$181.40	$181.40	$181.40
Purchase #7	$66.33	9.380%	$72.5518	$72.55	$72.55	$72.60
7 purchase totals =	$897.10		$966.5279	$966.52	$966.50	$966.70