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	$161.32	8.582%	$175.1645	$175.16	$175.15	$175.20
Purchase #2	$145.57	4.400%	$151.9751	$151.98	$152.00	$152.00
Purchase #3	$105.31	5.867%	$111.4885	$111.49	$111.50	$111.50
Purchase #4	$243.77	11.802%	$272.5397	$272.54	$272.55	$272.50
Purchase #5	$32.88	12.618%	$37.0288	$37.03	$37.05	$37.00
Purchase #6	$37.77	3.572%	$39.1191	$39.12	$39.10	$39.10
Purchase #7	$46.85	12.116%	$52.5263	$52.53	$52.55	$52.50
7 purchase totals =	$773.47		$839.8420	$839.85	$839.90	$839.80