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	$43.70	4.639%	$45.7272	$45.73	$45.75	$45.70
Purchase #2	$210.61	4.715%	$220.5403	$220.54	$220.55	$220.50
Purchase #3	$43.31	3.765%	$44.9406	$44.94	$44.95	$44.90
Purchase #4	$245.46	13.164%	$277.7724	$277.77	$277.75	$277.80
Purchase #5	$53.77	6.593%	$57.3151	$57.32	$57.30	$57.30
Purchase #6	$180.91	8.598%	$196.4646	$196.46	$196.45	$196.50
Purchase #7	$228.50	4.174%	$238.0376	$238.04	$238.05	$238.00
7 purchase totals =	$1,006.26		$1,080.7978	$1,080.80	$1,080.80	$1,080.70