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	$106.49	9.633%	$116.7482	$116.75	$116.75	$116.70
Purchase #2	$6.27	13.698%	$7.1289	$7.13	$7.15	$7.10
Purchase #3	$115.56	9.797%	$126.8814	$126.88	$126.90	$126.90
Purchase #4	$120.54	6.114%	$127.9098	$127.91	$127.90	$127.90
Purchase #5	$232.89	6.602%	$248.2654	$248.27	$248.25	$248.30
Purchase #6	$59.72	7.230%	$64.0378	$64.04	$64.05	$64.00
Purchase #7	$94.87	7.851%	$102.3182	$102.32	$102.30	$102.30
7 purchase totals =	$736.34		$793.2897	$793.30	$793.30	$793.20