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	$248.36	11.525%	$276.9835	$276.98	$277.00	$277.00
Purchase #2	$229.93	13.468%	$260.897	$260.90	$260.90	$260.90
Purchase #3	$243.70	12.589%	$274.3794	$274.38	$274.40	$274.40
Purchase #4	$10.88	7.504%	$11.6964	$11.70	$11.70	$11.70
Purchase #5	$29.93	5.650%	$31.621	$31.62	$31.60	$31.60
Purchase #6	$146.84	10.797%	$162.6943	$162.69	$162.70	$162.70
Purchase #7	$113.25	12.629%	$127.5523	$127.55	$127.55	$127.60
7 purchase totals =	$1,022.89		$1,145.8239	$1,145.82	$1,145.85	$1,145.90