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	$175.35	6.777%	$187.2335	$187.23	$187.25	$187.20
Purchase #2	$37.66	13.614%	$42.787	$42.79	$42.80	$42.80
Purchase #3	$125.71	8.223%	$136.0471	$136.05	$136.05	$136.00
Purchase #4	$74.92	11.283%	$83.3732	$83.37	$83.35	$83.40
Purchase #5	$54.50	13.169%	$61.6771	$61.68	$61.70	$61.70
Purchase #6	$99.82	6.648%	$106.456	$106.46	$106.45	$106.50
Purchase #7	$9.37	7.377%	$10.0612	$10.06	$10.05	$10.10
7 purchase totals =	$577.33		$627.6351	$627.64	$627.65	$627.70