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	$14.68	7.122%	$15.7255	$15.73	$15.75	$15.70
Purchase #2	$99.84	5.408%	$105.2393	$105.24	$105.25	$105.20
Purchase #3	$246.33	5.434%	$259.7156	$259.72	$259.70	$259.70
Purchase #4	$61.54	5.833%	$65.1296	$65.13	$65.15	$65.10
Purchase #5	$235.80	6.117%	$250.2239	$250.22	$250.20	$250.20
Purchase #6	$127.26	3.166%	$131.2891	$131.29	$131.30	$131.30
Purchase #7	$162.57	7.706%	$175.0976	$175.10	$175.10	$175.10
7 purchase totals =	$948.02		$1,002.4206	$1,002.43	$1,002.45	$1,002.30