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	$243.91	10.529%	$269.5913	$269.59	$269.60	$269.60
Purchase #2	$45.53	3.109%	$46.9455	$46.95	$46.95	$46.90
Purchase #3	$171.49	13.866%	$195.2688	$195.27	$195.25	$195.30
Purchase #4	$174.34	3.552%	$180.5326	$180.53	$180.55	$180.50
Purchase #5	$88.50	13.253%	$100.2289	$100.23	$100.25	$100.20
Purchase #6	$209.36	3.790%	$217.2947	$217.29	$217.30	$217.30
Purchase #7	$45.75	11.111%	$50.8333	$50.83	$50.85	$50.80
7 purchase totals =	$978.88		$1,060.6951	$1,060.69	$1,060.75	$1,060.60