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	$191.32	7.828%	$206.2965	$206.30	$206.30	$206.30
Purchase #2	$37.79	8.362%	$40.95	$40.95	$40.95	$41.00
Purchase #3	$43.76	4.165%	$45.5826	$45.58	$45.60	$45.60
Purchase #4	$142.88	7.261%	$153.2545	$153.25	$153.25	$153.30
Purchase #5	$30.95	9.198%	$33.7968	$33.80	$33.80	$33.80
Purchase #6	$82.69	3.737%	$85.7801	$85.78	$85.80	$85.80
Purchase #7	$31.61	3.586%	$32.7435	$32.74	$32.75	$32.70
7 purchase totals =	$561.00		$598.4040	$598.40	$598.45	$598.50