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	$217.56	6.853%	$232.4694	$232.47	$232.45	$232.50
Purchase #2	$167.95	7.263%	$180.1482	$180.15	$180.15	$180.10
Purchase #3	$62.37	8.139%	$67.4463	$67.45	$67.45	$67.40
Purchase #4	$45.95	6.584%	$48.9753	$48.98	$49.00	$49.00
Purchase #5	$162.33	12.618%	$182.8128	$182.81	$182.80	$182.80
Purchase #6	$201.48	11.125%	$223.8947	$223.89	$223.90	$223.90
Purchase #7	$111.65	8.180%	$120.783	$120.78	$120.80	$120.80
7 purchase totals =	$969.29		$1,056.5297	$1,056.53	$1,056.55	$1,056.50