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	$150.41	7.139%	$161.1478	$161.15	$161.15	$161.10
Purchase #2	$81.80	9.689%	$89.7256	$89.73	$89.75	$89.70
Purchase #3	$168.42	13.636%	$191.3858	$191.39	$191.40	$191.40
Purchase #4	$193.57	10.114%	$213.1477	$213.15	$213.15	$213.10
Purchase #5	$192.80	5.510%	$203.4233	$203.42	$203.40	$203.40
Purchase #6	$198.48	12.812%	$223.9093	$223.91	$223.90	$223.90
Purchase #7	$135.83	10.536%	$150.141	$150.14	$150.15	$150.10
7 purchase totals =	$1,121.31		$1,232.8805	$1,232.89	$1,232.90	$1,232.70