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	$172.93	4.501%	$180.7136	$180.71	$180.70	$180.70
Purchase #2	$206.98	4.651%	$216.6066	$216.61	$216.60	$216.60
Purchase #3	$79.60	11.265%	$88.5669	$88.57	$88.55	$88.60
Purchase #4	$174.62	11.672%	$195.0016	$195.00	$195.00	$195.00
Purchase #5	$76.25	9.298%	$83.3397	$83.34	$83.35	$83.30
Purchase #6	$42.76	5.561%	$45.1379	$45.14	$45.15	$45.10
Purchase #7	$185.90	12.645%	$209.4071	$209.41	$209.40	$209.40
7 purchase totals =	$939.04		$1,018.7734	$1,018.78	$1,018.75	$1,018.70