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	$197.33	7.396%	$211.9245	$211.92	$211.90	$211.90
Purchase #2	$188.97	8.177%	$204.4221	$204.42	$204.40	$204.40
Purchase #3	$57.35	13.696%	$65.2047	$65.20	$65.20	$65.20
Purchase #4	$63.86	5.406%	$67.3123	$67.31	$67.30	$67.30
Purchase #5	$18.37	11.541%	$20.4901	$20.49	$20.50	$20.50
Purchase #6	$150.73	9.701%	$165.3523	$165.35	$165.35	$165.40
Purchase #7	$228.81	6.696%	$244.1311	$244.13	$244.15	$244.10
7 purchase totals =	$905.42		$978.8371	$978.82	$978.80	$978.80