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	$211.60	11.848%	$236.6704	$236.67	$236.65	$236.70
Purchase #2	$236.66	9.374%	$258.8445	$258.84	$258.85	$258.80
Purchase #3	$218.56	10.370%	$241.2247	$241.22	$241.20	$241.20
Purchase #4	$247.28	8.221%	$267.6089	$267.61	$267.60	$267.60
Purchase #5	$48.30	11.164%	$53.6922	$53.69	$53.70	$53.70
Purchase #6	$40.41	12.321%	$45.3889	$45.39	$45.40	$45.40
Purchase #7	$109.91	12.570%	$123.7257	$123.73	$123.75	$123.70
7 purchase totals =	$1,112.72		$1,227.1553	$1,227.15	$1,227.15	$1,227.10