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	$102.36	3.171%	$105.6058	$105.61	$105.60	$105.60
Purchase #2	$170.39	11.404%	$189.8213	$189.82	$189.80	$189.80
Purchase #3	$119.79	10.678%	$132.5812	$132.58	$132.60	$132.60
Purchase #4	$241.69	9.306%	$264.1817	$264.18	$264.20	$264.20
Purchase #5	$199.26	5.675%	$210.568	$210.57	$210.55	$210.60
Purchase #6	$34.30	11.723%	$38.321	$38.32	$38.30	$38.30
Purchase #7	$85.34	7.440%	$91.6893	$91.69	$91.70	$91.70
7 purchase totals =	$953.13		$1,032.7683	$1,032.77	$1,032.75	$1,032.80