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	$67.28	12.257%	$75.5265	$75.53	$75.55	$75.50
Purchase #2	$109.25	3.164%	$112.7067	$112.71	$112.70	$112.70
Purchase #3	$9.61	5.684%	$10.1562	$10.16	$10.15	$10.20
Purchase #4	$78.48	6.840%	$83.848	$83.85	$83.85	$83.80
Purchase #5	$136.71	4.711%	$143.1504	$143.15	$143.15	$143.20
Purchase #6	$28.95	11.766%	$32.3563	$32.36	$32.35	$32.40
Purchase #7	$142.69	9.594%	$156.3797	$156.38	$156.40	$156.40
7 purchase totals =	$572.97		$614.1238	$614.14	$614.15	$614.20