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	$50.50	5.337%	$53.1952	$53.20	$53.20	$53.20
Purchase #2	$59.61	4.635%	$62.3729	$62.37	$62.35	$62.40
Purchase #3	$212.69	11.459%	$237.0621	$237.06	$237.05	$237.10
Purchase #4	$204.53	10.700%	$226.4147	$226.41	$226.40	$226.40
Purchase #5	$89.54	11.130%	$99.5058	$99.51	$99.50	$99.50
Purchase #6	$198.40	7.806%	$213.8871	$213.89	$213.90	$213.90
Purchase #7	$240.82	5.263%	$253.4944	$253.49	$253.50	$253.50
7 purchase totals =	$1,056.09		$1,145.9322	$1,145.93	$1,145.90	$1,146.00