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	$107.26	5.405%	$113.0574	$113.06	$113.05	$113.10
Purchase #2	$188.83	11.132%	$209.8506	$209.85	$209.85	$209.90
Purchase #3	$151.90	10.846%	$168.3751	$168.38	$168.40	$168.40
Purchase #4	$197.55	12.478%	$222.2003	$222.20	$222.20	$222.20
Purchase #5	$248.84	10.173%	$274.1545	$274.15	$274.15	$274.20
Purchase #6	$33.82	7.634%	$36.4018	$36.40	$36.40	$36.40
Purchase #7	$117.89	11.857%	$131.8682	$131.87	$131.85	$131.90
7 purchase totals =	$1,046.09		$1,155.9079	$1,155.91	$1,155.90	$1,156.10