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	$225.47	10.629%	$249.4352	$249.44	$249.45	$249.40
Purchase #2	$249.41	8.485%	$270.5724	$270.57	$270.55	$270.60
Purchase #3	$76.95	7.726%	$82.8952	$82.90	$82.90	$82.90
Purchase #4	$209.57	6.678%	$223.5651	$223.57	$223.55	$223.60
Purchase #5	$17.42	4.190%	$18.1499	$18.15	$18.15	$18.10
Purchase #6	$76.42	12.403%	$85.8984	$85.90	$85.90	$85.90
Purchase #7	$201.49	8.681%	$218.9813	$218.98	$219.00	$219.00
7 purchase totals =	$1,056.73		$1,149.4975	$1,149.51	$1,149.50	$1,149.50