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	$52.34	12.753%	$59.0149	$59.01	$59.00	$59.00
Purchase #2	$162.75	7.668%	$175.2297	$175.23	$175.25	$175.20
Purchase #3	$80.81	3.786%	$83.8695	$83.87	$83.85	$83.90
Purchase #4	$185.31	3.130%	$191.1102	$191.11	$191.10	$191.10
Purchase #5	$240.28	7.667%	$258.7023	$258.70	$258.70	$258.70
Purchase #6	$47.82	3.236%	$49.3675	$49.37	$49.35	$49.40
Purchase #7	$56.43	5.135%	$59.3277	$59.33	$59.35	$59.30
7 purchase totals =	$825.74		$876.6218	$876.62	$876.60	$876.60