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	$96.35	5.518%	$101.6666	$101.67	$101.65	$101.70
Purchase #2	$33.71	12.586%	$37.9527	$37.95	$37.95	$38.00
Purchase #3	$123.38	9.240%	$134.7803	$134.78	$134.80	$134.80
Purchase #4	$235.96	7.657%	$254.0275	$254.03	$254.05	$254.00
Purchase #5	$238.34	10.321%	$262.9391	$262.94	$262.95	$262.90
Purchase #6	$170.47	8.851%	$185.5583	$185.56	$185.55	$185.60
Purchase #7	$185.65	12.213%	$208.3234	$208.32	$208.30	$208.30
7 purchase totals =	$1,083.86		$1,185.2479	$1,185.25	$1,185.25	$1,185.30