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	$207.43	11.598%	$231.4877	$231.49	$231.50	$231.50
Purchase #2	$233.80	5.770%	$247.2903	$247.29	$247.30	$247.30
Purchase #3	$159.59	13.107%	$180.5075	$180.51	$180.50	$180.50
Purchase #4	$55.30	7.445%	$59.4171	$59.42	$59.40	$59.40
Purchase #5	$170.67	3.354%	$176.3943	$176.39	$176.40	$176.40
Purchase #6	$44.65	5.580%	$47.1415	$47.14	$47.15	$47.10
Purchase #7	$125.71	13.170%	$142.266	$142.27	$142.25	$142.30
7 purchase totals =	$997.15		$1,084.5044	$1,084.51	$1,084.50	$1,084.50