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	$197.59	13.388%	$224.0433	$224.04	$224.05	$224.00
Purchase #2	$148.79	6.165%	$157.9629	$157.96	$157.95	$158.00
Purchase #3	$191.54	9.401%	$209.5467	$209.55	$209.55	$209.50
Purchase #4	$141.39	12.848%	$159.5558	$159.56	$159.55	$159.60
Purchase #5	$71.38	9.289%	$78.0105	$78.01	$78.00	$78.00
Purchase #6	$128.88	8.742%	$140.1467	$140.15	$140.15	$140.10
Purchase #7	$161.65	6.352%	$171.918	$171.92	$171.90	$171.90
7 purchase totals =	$1,041.22		$1,141.1839	$1,141.19	$1,141.15	$1,141.10