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	$10.37	5.812%	$10.9727	$10.97	$10.95	$11.00
Purchase #2	$63.31	13.307%	$71.7347	$71.73	$71.75	$71.70
Purchase #3	$130.83	4.825%	$137.1425	$137.14	$137.15	$137.10
Purchase #4	$202.56	9.146%	$221.0861	$221.09	$221.10	$221.10
Purchase #5	$26.44	9.234%	$28.8815	$28.88	$28.90	$28.90
Purchase #6	$78.46	4.336%	$81.862	$81.86	$81.85	$81.90
Purchase #7	$189.67	13.433%	$215.1484	$215.15	$215.15	$215.10
7 purchase totals =	$701.64		$766.8279	$766.82	$766.85	$766.80