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	$66.44	11.240%	$73.9079	$73.91	$73.90	$73.90
Purchase #2	$107.90	5.234%	$113.5475	$113.55	$113.55	$113.50
Purchase #3	$67.68	5.597%	$71.468	$71.47	$71.45	$71.50
Purchase #4	$53.31	10.642%	$58.9833	$58.98	$59.00	$59.00
Purchase #5	$132.72	9.142%	$144.8533	$144.85	$144.85	$144.90
Purchase #6	$242.83	4.775%	$254.4251	$254.43	$254.45	$254.40
Purchase #7	$80.47	11.729%	$89.9083	$89.91	$89.90	$89.90
7 purchase totals =	$751.35		$807.0934	$807.10	$807.10	$807.10