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	$126.74	3.679%	$131.4028	$131.40	$131.40	$131.40
Purchase #2	$160.76	5.783%	$170.0568	$170.06	$170.05	$170.10
Purchase #3	$218.59	11.235%	$243.1486	$243.15	$243.15	$243.10
Purchase #4	$149.98	4.221%	$156.3107	$156.31	$156.30	$156.30
Purchase #5	$247.67	10.734%	$274.2549	$274.25	$274.25	$274.30
Purchase #6	$23.92	6.553%	$25.4875	$25.49	$25.50	$25.50
Purchase #7	$41.90	7.728%	$45.138	$45.14	$45.15	$45.10
7 purchase totals =	$969.56		$1,045.7993	$1,045.80	$1,045.80	$1,045.80