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	$165.96	7.341%	$178.1431	$178.14	$178.15	$178.10
Purchase #2	$171.78	10.699%	$190.1587	$190.16	$190.15	$190.20
Purchase #3	$199.59	7.287%	$214.1341	$214.13	$214.15	$214.10
Purchase #4	$60.30	11.512%	$67.2417	$67.24	$67.25	$67.20
Purchase #5	$136.63	11.539%	$152.3957	$152.40	$152.40	$152.40
Purchase #6	$117.33	6.159%	$124.5564	$124.56	$124.55	$124.60
Purchase #7	$131.97	8.490%	$143.1743	$143.17	$143.15	$143.20
7 purchase totals =	$983.56		$1,069.8040	$1,069.80	$1,069.80	$1,069.80