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	$97.42	12.563%	$109.6589	$109.66	$109.65	$109.70
Purchase #2	$89.91	10.210%	$99.0898	$99.09	$99.10	$99.10
Purchase #3	$123.82	3.695%	$128.3951	$128.40	$128.40	$128.40
Purchase #4	$124.79	4.328%	$130.1909	$130.19	$130.20	$130.20
Purchase #5	$209.36	11.641%	$233.7316	$233.73	$233.75	$233.70
Purchase #6	$57.94	12.868%	$65.3957	$65.40	$65.40	$65.40
Purchase #7	$124.33	6.454%	$132.3543	$132.35	$132.35	$132.40
7 purchase totals =	$827.57		$898.8163	$898.82	$898.85	$898.90