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	$161.55	3.448%	$167.1202	$167.12	$167.10	$167.10
Purchase #2	$155.38	10.319%	$171.4137	$171.41	$171.40	$171.40
Purchase #3	$31.26	5.474%	$32.9712	$32.97	$32.95	$33.00
Purchase #4	$71.28	8.143%	$77.0843	$77.08	$77.10	$77.10
Purchase #5	$29.56	13.702%	$33.6103	$33.61	$33.60	$33.60
Purchase #6	$104.30	7.448%	$112.0683	$112.07	$112.05	$112.10
Purchase #7	$78.88	4.532%	$82.4548	$82.45	$82.45	$82.50
7 purchase totals =	$632.21		$676.7228	$676.71	$676.65	$676.80