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	$13.32	5.847%	$14.0988	$14.10	$14.10	$14.10
Purchase #2	$65.26	10.114%	$71.8604	$71.86	$71.85	$71.90
Purchase #3	$113.93	7.225%	$122.1614	$122.16	$122.15	$122.20
Purchase #4	$96.96	12.530%	$109.1091	$109.11	$109.10	$109.10
Purchase #5	$225.79	13.114%	$255.4001	$255.40	$255.40	$255.40
Purchase #6	$236.59	10.389%	$261.1693	$261.17	$261.15	$261.20
Purchase #7	$171.73	10.565%	$189.8733	$189.87	$189.85	$189.90
7 purchase totals =	$923.58		$1,023.6724	$1,023.67	$1,023.60	$1,023.80