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	$146.53	8.767%	$159.3763	$159.38	$159.40	$159.40
Purchase #2	$213.45	9.294%	$233.288	$233.29	$233.30	$233.30
Purchase #3	$176.92	5.821%	$187.2185	$187.22	$187.20	$187.20
Purchase #4	$95.39	11.631%	$106.4848	$106.48	$106.50	$106.50
Purchase #5	$92.78	13.688%	$105.4797	$105.48	$105.50	$105.50
Purchase #6	$36.69	12.612%	$41.3173	$41.32	$41.30	$41.30
Purchase #7	$237.68	11.399%	$264.7731	$264.77	$264.75	$264.80
7 purchase totals =	$999.44		$1,097.9377	$1,097.94	$1,097.95	$1,098.00