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	$116.69	12.708%	$131.519	$131.52	$131.50	$131.50
Purchase #2	$180.45	6.339%	$191.8887	$191.89	$191.90	$191.90
Purchase #3	$147.84	11.823%	$165.3191	$165.32	$165.30	$165.30
Purchase #4	$250.48	3.316%	$258.7859	$258.79	$258.80	$258.80
Purchase #5	$22.77	13.857%	$25.9252	$25.93	$25.95	$25.90
Purchase #6	$39.73	13.326%	$45.0244	$45.02	$45.00	$45.00
Purchase #7	$184.32	4.428%	$192.4817	$192.48	$192.50	$192.50
7 purchase totals =	$942.28		$1,010.9440	$1,010.95	$1,010.95	$1,010.90