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	$105.29	11.378%	$117.2699	$117.27	$117.25	$117.30
Purchase #2	$169.75	11.145%	$188.6686	$188.67	$188.65	$188.70
Purchase #3	$78.29	10.152%	$86.238	$86.24	$86.25	$86.20
Purchase #4	$36.91	10.256%	$40.6955	$40.70	$40.70	$40.70
Purchase #5	$178.98	5.502%	$188.8275	$188.83	$188.85	$188.80
Purchase #6	$196.25	3.682%	$203.4759	$203.48	$203.50	$203.50
Purchase #7	$96.30	10.296%	$106.215	$106.22	$106.20	$106.20
7 purchase totals =	$861.77		$931.3904	$931.41	$931.40	$931.40