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	$229.89	8.524%	$249.4858	$249.49	$249.50	$249.50
Purchase #2	$228.78	9.285%	$250.0222	$250.02	$250.00	$250.00
Purchase #3	$153.85	4.675%	$161.0425	$161.04	$161.05	$161.00
Purchase #4	$152.32	9.178%	$166.2999	$166.30	$166.30	$166.30
Purchase #5	$11.63	5.637%	$12.2856	$12.29	$12.30	$12.30
Purchase #6	$59.80	6.237%	$63.5297	$63.53	$63.55	$63.50
Purchase #7	$168.89	3.115%	$174.1509	$174.15	$174.15	$174.20
7 purchase totals =	$1,005.16		$1,076.8166	$1,076.82	$1,076.85	$1,076.80