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	$57.68	7.817%	$62.1888	$62.19	$62.20	$62.20
Purchase #2	$213.95	13.466%	$242.7605	$242.76	$242.75	$242.80
Purchase #3	$89.65	11.733%	$100.1686	$100.17	$100.15	$100.20
Purchase #4	$211.35	9.712%	$231.8763	$231.88	$231.90	$231.90
Purchase #5	$154.73	8.506%	$167.8913	$167.89	$167.90	$167.90
Purchase #6	$220.78	3.874%	$229.333	$229.33	$229.35	$229.30
Purchase #7	$139.83	11.745%	$156.253	$156.25	$156.25	$156.30
7 purchase totals =	$1,087.97		$1,190.4715	$1,190.47	$1,190.50	$1,190.60