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	$108.49	8.669%	$117.895	$117.90	$117.90	$117.90
Purchase #2	$73.66	11.454%	$82.097	$82.10	$82.10	$82.10
Purchase #3	$9.70	4.586%	$10.1448	$10.14	$10.15	$10.10
Purchase #4	$139.51	10.274%	$153.8433	$153.84	$153.85	$153.80
Purchase #5	$100.64	4.120%	$104.7864	$104.79	$104.80	$104.80
Purchase #6	$40.50	7.316%	$43.463	$43.46	$43.45	$43.50
Purchase #7	$138.80	9.825%	$152.4371	$152.44	$152.45	$152.40
7 purchase totals =	$611.30		$664.6666	$664.67	$664.70	$664.60