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	$174.77	12.306%	$196.2772	$196.28	$196.30	$196.30
Purchase #2	$131.67	7.459%	$141.4913	$141.49	$141.50	$141.50
Purchase #3	$120.93	10.720%	$133.8937	$133.89	$133.90	$133.90
Purchase #4	$165.48	4.870%	$173.5389	$173.54	$173.55	$173.50
Purchase #5	$26.71	6.485%	$28.4421	$28.44	$28.45	$28.40
Purchase #6	$67.99	4.856%	$71.2916	$71.29	$71.30	$71.30
Purchase #7	$128.36	7.866%	$138.4568	$138.46	$138.45	$138.50
7 purchase totals =	$815.91		$883.3916	$883.39	$883.45	$883.40