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	$57.45	11.349%	$63.97	$63.97	$63.95	$64.00
Purchase #2	$108.84	4.771%	$114.0328	$114.03	$114.05	$114.00
Purchase #3	$153.55	8.707%	$166.9196	$166.92	$166.90	$166.90
Purchase #4	$74.41	11.365%	$82.8667	$82.87	$82.85	$82.90
Purchase #5	$167.63	6.784%	$179.002	$179.00	$179.00	$179.00
Purchase #6	$72.73	12.841%	$82.0693	$82.07	$82.05	$82.10
Purchase #7	$55.99	6.170%	$59.4446	$59.44	$59.45	$59.40
7 purchase totals =	$690.60		$748.3050	$748.30	$748.25	$748.30