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	$187.53	4.829%	$196.5858	$196.59	$196.60	$196.60
Purchase #2	$86.57	6.442%	$92.1468	$92.15	$92.15	$92.10
Purchase #3	$27.40	6.702%	$29.2363	$29.24	$29.25	$29.20
Purchase #4	$145.25	8.379%	$157.4205	$157.42	$157.40	$157.40
Purchase #5	$71.26	9.694%	$78.1679	$78.17	$78.15	$78.20
Purchase #6	$55.88	4.372%	$58.3231	$58.32	$58.30	$58.30
Purchase #7	$89.82	11.157%	$99.8412	$99.84	$99.85	$99.80
7 purchase totals =	$663.71		$711.7216	$711.73	$711.70	$711.60