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	$166.29	10.703%	$184.088	$184.09	$184.10	$184.10
Purchase #2	$51.46	8.812%	$55.9947	$55.99	$56.00	$56.00
Purchase #3	$20.25	10.152%	$22.3058	$22.31	$22.30	$22.30
Purchase #4	$56.86	4.586%	$59.4676	$59.47	$59.45	$59.50
Purchase #5	$17.95	12.721%	$20.2334	$20.23	$20.25	$20.20
Purchase #6	$134.31	5.272%	$141.3908	$141.39	$141.40	$141.40
Purchase #7	$200.42	10.820%	$222.1054	$222.11	$222.10	$222.10
7 purchase totals =	$647.54		$705.5857	$705.59	$705.60	$705.60