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	$244.33	10.475%	$269.9236	$269.92	$269.90	$269.90
Purchase #2	$180.55	6.186%	$191.7188	$191.72	$191.70	$191.70
Purchase #3	$218.69	11.466%	$243.765	$243.77	$243.75	$243.80
Purchase #4	$206.48	9.806%	$226.7274	$226.73	$226.75	$226.70
Purchase #5	$86.73	3.567%	$89.8237	$89.82	$89.80	$89.80
Purchase #6	$28.89	12.236%	$32.425	$32.43	$32.45	$32.40
Purchase #7	$18.67	13.321%	$21.157	$21.16	$21.15	$21.20
7 purchase totals =	$984.34		$1,075.5405	$1,075.55	$1,075.50	$1,075.50