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	$165.64	12.200%	$185.8481	$185.85	$185.85	$185.80
Purchase #2	$68.89	3.395%	$71.2288	$71.23	$71.25	$71.20
Purchase #3	$191.72	8.531%	$208.0756	$208.08	$208.10	$208.10
Purchase #4	$140.70	4.736%	$147.3636	$147.36	$147.35	$147.40
Purchase #5	$114.25	11.497%	$127.3853	$127.39	$127.40	$127.40
Purchase #6	$248.56	7.192%	$266.4364	$266.44	$266.45	$266.40
Purchase #7	$47.93	10.261%	$52.8481	$52.85	$52.85	$52.80
7 purchase totals =	$977.69		$1,059.1859	$1,059.20	$1,059.25	$1,059.10