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	$146.50	13.868%	$166.8166	$166.82	$166.80	$166.80
Purchase #2	$16.87	12.123%	$18.9152	$18.92	$18.90	$18.90
Purchase #3	$17.91	11.289%	$19.9319	$19.93	$19.95	$19.90
Purchase #4	$44.25	13.709%	$50.3162	$50.32	$50.30	$50.30
Purchase #5	$11.27	4.271%	$11.7513	$11.75	$11.75	$11.80
Purchase #6	$42.43	6.309%	$45.1069	$45.11	$45.10	$45.10
Purchase #7	$188.69	6.258%	$200.4982	$200.50	$200.50	$200.50
7 purchase totals =	$467.92		$513.3363	$513.35	$513.30	$513.30