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	$178.77	8.139%	$193.3201	$193.32	$193.30	$193.30
Purchase #2	$164.72	12.570%	$185.4253	$185.43	$185.45	$185.40
Purchase #3	$36.37	4.225%	$37.9066	$37.91	$37.90	$37.90
Purchase #4	$56.83	12.660%	$64.0247	$64.02	$64.00	$64.00
Purchase #5	$145.78	8.594%	$158.3083	$158.31	$158.30	$158.30
Purchase #6	$156.67	8.263%	$169.6156	$169.62	$169.60	$169.60
Purchase #7	$184.63	13.384%	$209.3409	$209.34	$209.35	$209.30
7 purchase totals =	$923.77		$1,017.9415	$1,017.95	$1,017.90	$1,017.80