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	$209.35	13.404%	$237.4113	$237.41	$237.40	$237.40
Purchase #2	$247.43	7.431%	$265.8165	$265.82	$265.80	$265.80
Purchase #3	$29.38	7.108%	$31.4683	$31.47	$31.45	$31.50
Purchase #4	$6.73	3.411%	$6.9596	$6.96	$6.95	$7.00
Purchase #5	$205.89	7.864%	$222.0812	$222.08	$222.10	$222.10
Purchase #6	$118.53	7.439%	$127.3474	$127.35	$127.35	$127.30
Purchase #7	$164.29	11.562%	$183.2852	$183.29	$183.30	$183.30
7 purchase totals =	$981.60		$1,074.3695	$1,074.38	$1,074.35	$1,074.40