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	$85.94	3.735%	$89.1499	$89.15	$89.15	$89.10
Purchase #2	$28.46	9.428%	$31.1432	$31.14	$31.15	$31.10
Purchase #3	$16.76	3.787%	$17.3947	$17.39	$17.40	$17.40
Purchase #4	$21.62	11.353%	$24.0745	$24.07	$24.05	$24.10
Purchase #5	$38.91	12.527%	$43.7843	$43.78	$43.80	$43.80
Purchase #6	$133.61	6.867%	$142.785	$142.79	$142.80	$142.80
Purchase #7	$112.71	5.388%	$118.7828	$118.78	$118.80	$118.80
7 purchase totals =	$438.01		$467.1144	$467.10	$467.15	$467.10