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	$103.92	7.336%	$111.5436	$111.54	$111.55	$111.50
Purchase #2	$175.37	6.848%	$187.3793	$187.38	$187.40	$187.40
Purchase #3	$187.97	10.287%	$207.3065	$207.31	$207.30	$207.30
Purchase #4	$216.62	12.768%	$244.278	$244.28	$244.30	$244.30
Purchase #5	$71.73	12.585%	$80.7572	$80.76	$80.75	$80.80
Purchase #6	$143.79	10.728%	$159.2158	$159.22	$159.20	$159.20
Purchase #7	$154.26	11.719%	$172.3377	$172.34	$172.35	$172.30
7 purchase totals =	$1,053.66		$1,162.8181	$1,162.83	$1,162.85	$1,162.80