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	$53.73	6.263%	$57.0951	$57.10	$57.10	$57.10
Purchase #2	$6.69	11.744%	$7.4757	$7.48	$7.50	$7.50
Purchase #3	$176.94	7.441%	$190.1061	$190.11	$190.10	$190.10
Purchase #4	$229.79	11.106%	$255.3105	$255.31	$255.30	$255.30
Purchase #5	$101.80	3.364%	$105.2246	$105.22	$105.20	$105.20
Purchase #6	$161.96	12.419%	$182.0738	$182.07	$182.05	$182.10
Purchase #7	$237.92	13.283%	$269.5229	$269.52	$269.50	$269.50
7 purchase totals =	$968.83		$1,066.8087	$1,066.81	$1,066.75	$1,066.80