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	$170.91	10.240%	$188.4112	$188.41	$188.40	$188.40
Purchase #2	$166.25	4.761%	$174.1652	$174.17	$174.15	$174.20
Purchase #3	$34.88	7.262%	$37.413	$37.41	$37.40	$37.40
Purchase #4	$241.50	11.735%	$269.84	$269.84	$269.85	$269.80
Purchase #5	$165.78	10.577%	$183.3146	$183.31	$183.30	$183.30
Purchase #6	$82.43	8.572%	$89.4959	$89.50	$89.50	$89.50
Purchase #7	$12.37	4.339%	$12.9067	$12.91	$12.90	$12.90
7 purchase totals =	$874.12		$955.5466	$955.55	$955.50	$955.50