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	$119.39	9.205%	$130.3798	$130.38	$130.40	$130.40
Purchase #2	$247.86	3.735%	$257.1176	$257.12	$257.10	$257.10
Purchase #3	$158.96	3.826%	$165.0418	$165.04	$165.05	$165.00
Purchase #4	$162.31	10.693%	$179.6658	$179.67	$179.65	$179.70
Purchase #5	$27.56	3.410%	$28.4998	$28.50	$28.50	$28.50
Purchase #6	$30.76	13.427%	$34.8901	$34.89	$34.90	$34.90
Purchase #7	$195.96	6.717%	$209.1226	$209.12	$209.10	$209.10
7 purchase totals =	$942.80		$1,004.7175	$1,004.72	$1,004.70	$1,004.70