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	$108.34	3.440%	$112.0669	$112.07	$112.05	$112.10
Purchase #2	$58.88	11.356%	$65.5664	$65.57	$65.55	$65.60
Purchase #3	$39.73	7.645%	$42.7674	$42.77	$42.75	$42.80
Purchase #4	$147.52	10.304%	$162.7205	$162.72	$162.70	$162.70
Purchase #5	$32.26	10.665%	$35.7005	$35.70	$35.70	$35.70
Purchase #6	$172.73	13.540%	$196.1176	$196.12	$196.10	$196.10
Purchase #7	$245.76	12.588%	$276.6963	$276.70	$276.70	$276.70
7 purchase totals =	$805.22		$891.6356	$891.65	$891.55	$891.70