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	$166.39	5.135%	$174.9341	$174.93	$174.95	$174.90
Purchase #2	$188.27	11.420%	$209.7704	$209.77	$209.75	$209.80
Purchase #3	$97.42	13.472%	$110.5444	$110.54	$110.55	$110.50
Purchase #4	$203.57	13.668%	$231.3939	$231.39	$231.40	$231.40
Purchase #5	$108.90	6.377%	$115.8446	$115.84	$115.85	$115.80
Purchase #6	$161.31	6.219%	$171.3419	$171.34	$171.35	$171.30
Purchase #7	$64.89	11.630%	$72.4367	$72.44	$72.45	$72.40
7 purchase totals =	$990.75		$1,086.2660	$1,086.25	$1,086.30	$1,086.10