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	$106.34	5.103%	$111.7665	$111.77	$111.75	$111.80
Purchase #2	$181.52	8.640%	$197.2033	$197.20	$197.20	$197.20
Purchase #3	$130.27	9.661%	$142.8554	$142.86	$142.85	$142.90
Purchase #4	$103.63	5.593%	$109.426	$109.43	$109.45	$109.40
Purchase #5	$235.82	13.467%	$267.5779	$267.58	$267.60	$267.60
Purchase #6	$42.73	11.540%	$47.661	$47.66	$47.65	$47.70
Purchase #7	$57.46	8.406%	$62.2901	$62.29	$62.30	$62.30
7 purchase totals =	$857.77		$938.7802	$938.79	$938.80	$938.90