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	$111.97	5.235%	$117.8316	$117.83	$117.85	$117.80
Purchase #2	$96.39	9.550%	$105.5952	$105.60	$105.60	$105.60
Purchase #3	$89.84	10.640%	$99.399	$99.40	$99.40	$99.40
Purchase #4	$141.65	3.867%	$147.1276	$147.13	$147.15	$147.10
Purchase #5	$19.47	7.277%	$20.8868	$20.89	$20.90	$20.90
Purchase #6	$101.47	3.481%	$105.0022	$105.00	$105.00	$105.00
Purchase #7	$13.67	7.665%	$14.7178	$14.72	$14.70	$14.70
7 purchase totals =	$574.46		$610.5602	$610.57	$610.60	$610.50