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	$25.63	4.745%	$26.8461	$26.85	$26.85	$26.80
Purchase #2	$67.96	12.595%	$76.5196	$76.52	$76.50	$76.50
Purchase #3	$218.38	13.673%	$248.2391	$248.24	$248.25	$248.20
Purchase #4	$95.75	4.338%	$99.9036	$99.90	$99.90	$99.90
Purchase #5	$153.29	3.614%	$158.8299	$158.83	$158.85	$158.80
Purchase #6	$216.57	9.614%	$237.391	$237.39	$237.40	$237.40
Purchase #7	$196.70	11.219%	$218.7678	$218.77	$218.75	$218.80
7 purchase totals =	$974.28		$1,066.4971	$1,066.50	$1,066.50	$1,066.40