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	$69.45	6.342%	$73.8545	$73.85	$73.85	$73.90
Purchase #2	$208.32	11.630%	$232.5476	$232.55	$232.55	$232.50
Purchase #3	$85.66	4.399%	$89.4282	$89.43	$89.45	$89.40
Purchase #4	$230.51	3.428%	$238.4119	$238.41	$238.40	$238.40
Purchase #5	$101.72	4.686%	$106.4866	$106.49	$106.50	$106.50
Purchase #6	$11.36	13.686%	$12.9147	$12.91	$12.90	$12.90
Purchase #7	$45.55	9.599%	$49.9223	$49.92	$49.90	$49.90
7 purchase totals =	$752.57		$803.5658	$803.56	$803.55	$803.50