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	$83.38	3.526%	$86.32	$86.32	$86.30	$86.30
Purchase #2	$137.77	3.610%	$142.7435	$142.74	$142.75	$142.70
Purchase #3	$154.61	5.162%	$162.591	$162.59	$162.60	$162.60
Purchase #4	$98.75	7.416%	$106.0733	$106.07	$106.05	$106.10
Purchase #5	$37.39	7.737%	$40.2829	$40.28	$40.30	$40.30
Purchase #6	$130.43	8.575%	$141.6144	$141.61	$141.60	$141.60
Purchase #7	$143.45	7.145%	$153.6995	$153.70	$153.70	$153.70
7 purchase totals =	$785.78		$833.3246	$833.31	$833.30	$833.30