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	$232.84	13.496%	$264.2641	$264.26	$264.25	$264.30
Purchase #2	$151.56	9.387%	$165.7869	$165.79	$165.80	$165.80
Purchase #3	$126.64	8.254%	$137.0929	$137.09	$137.10	$137.10
Purchase #4	$77.76	6.714%	$82.9808	$82.98	$83.00	$83.00
Purchase #5	$43.79	4.474%	$45.7492	$45.75	$45.75	$45.70
Purchase #6	$99.26	13.234%	$112.3961	$112.40	$112.40	$112.40
Purchase #7	$114.38	11.377%	$127.393	$127.39	$127.40	$127.40
7 purchase totals =	$846.23		$935.6630	$935.66	$935.70	$935.70