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	$107.88	3.738%	$111.9126	$111.91	$111.90	$111.90
Purchase #2	$107.93	11.165%	$119.9804	$119.98	$120.00	$120.00
Purchase #3	$128.61	12.851%	$145.1377	$145.14	$145.15	$145.10
Purchase #4	$9.33	6.283%	$9.9162	$9.92	$9.90	$9.90
Purchase #5	$37.81	13.478%	$42.906	$42.91	$42.90	$42.90
Purchase #6	$29.79	9.497%	$32.6192	$32.62	$32.60	$32.60
Purchase #7	$243.36	8.162%	$263.223	$263.22	$263.20	$263.20
7 purchase totals =	$664.71		$725.6951	$725.70	$725.65	$725.60