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	$129.63	10.679%	$143.4732	$143.47	$143.45	$143.50
Purchase #2	$128.45	3.464%	$132.8995	$132.90	$132.90	$132.90
Purchase #3	$108.91	5.559%	$114.9643	$114.96	$114.95	$115.00
Purchase #4	$88.57	12.633%	$99.759	$99.76	$99.75	$99.80
Purchase #5	$127.72	11.214%	$142.0425	$142.04	$142.05	$142.00
Purchase #6	$102.65	13.759%	$116.7736	$116.77	$116.75	$116.80
Purchase #7	$190.38	4.374%	$198.7072	$198.71	$198.70	$198.70
7 purchase totals =	$876.31		$948.6193	$948.61	$948.55	$948.70