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	$40.47	5.437%	$42.6704	$42.67	$42.65	$42.70
Purchase #2	$183.51	4.281%	$191.3661	$191.37	$191.35	$191.40
Purchase #3	$11.62	13.122%	$13.1448	$13.14	$13.15	$13.10
Purchase #4	$229.67	8.571%	$249.355	$249.36	$249.35	$249.40
Purchase #5	$193.44	11.363%	$215.4206	$215.42	$215.40	$215.40
Purchase #6	$182.49	6.662%	$194.6475	$194.65	$194.65	$194.60
Purchase #7	$146.51	5.728%	$154.9021	$154.90	$154.90	$154.90
7 purchase totals =	$987.71		$1,061.5065	$1,061.51	$1,061.45	$1,061.50