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	$17.43	5.279%	$18.3501	$18.35	$18.35	$18.40
Purchase #2	$70.32	4.560%	$73.5266	$73.53	$73.55	$73.50
Purchase #3	$18.48	11.802%	$20.661	$20.66	$20.65	$20.70
Purchase #4	$155.89	5.659%	$164.7118	$164.71	$164.70	$164.70
Purchase #5	$112.31	9.383%	$122.848	$122.85	$122.85	$122.80
Purchase #6	$211.37	5.180%	$222.319	$222.32	$222.30	$222.30
Purchase #7	$246.51	10.215%	$271.691	$271.69	$271.70	$271.70
7 purchase totals =	$832.31		$894.1075	$894.11	$894.10	$894.10