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	$165.89	5.548%	$175.0936	$175.09	$175.10	$175.10
Purchase #2	$179.41	5.644%	$189.5359	$189.54	$189.55	$189.50
Purchase #3	$184.70	4.229%	$192.511	$192.51	$192.50	$192.50
Purchase #4	$142.35	11.446%	$158.6434	$158.64	$158.65	$158.60
Purchase #5	$102.72	6.677%	$109.5786	$109.58	$109.60	$109.60
Purchase #6	$234.75	3.851%	$243.7902	$243.79	$243.80	$243.80
Purchase #7	$247.72	6.133%	$262.9127	$262.91	$262.90	$262.90
7 purchase totals =	$1,257.54		$1,332.0654	$1,332.06	$1,332.10	$1,332.00