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	$92.48	9.642%	$101.3969	$101.40	$101.40	$101.40
Purchase #2	$213.32	7.167%	$228.6086	$228.61	$228.60	$228.60
Purchase #3	$220.89	5.663%	$233.399	$233.40	$233.40	$233.40
Purchase #4	$208.60	10.336%	$230.1609	$230.16	$230.15	$230.20
Purchase #5	$79.94	12.224%	$89.7119	$89.71	$89.70	$89.70
Purchase #6	$105.91	11.544%	$118.1363	$118.14	$118.15	$118.10
Purchase #7	$38.41	7.259%	$41.1982	$41.20	$41.20	$41.20
7 purchase totals =	$959.55		$1,042.6118	$1,042.62	$1,042.60	$1,042.60