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	$207.35	11.629%	$231.4627	$231.46	$231.45	$231.50
Purchase #2	$18.35	9.140%	$20.0272	$20.03	$20.05	$20.00
Purchase #3	$226.59	7.295%	$243.1197	$243.12	$243.10	$243.10
Purchase #4	$104.41	6.195%	$110.8782	$110.88	$110.90	$110.90
Purchase #5	$74.92	4.699%	$78.4405	$78.44	$78.45	$78.40
Purchase #6	$222.50	12.800%	$250.98	$250.98	$251.00	$251.00
Purchase #7	$71.82	7.375%	$77.1167	$77.12	$77.10	$77.10
7 purchase totals =	$925.94		$1,012.0250	$1,012.03	$1,012.05	$1,012.00