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	$64.69	12.423%	$72.7264	$72.73	$72.75	$72.70
Purchase #2	$181.92	12.438%	$204.5472	$204.55	$204.55	$204.50
Purchase #3	$48.84	10.323%	$53.8818	$53.88	$53.90	$53.90
Purchase #4	$42.27	13.255%	$47.8729	$47.87	$47.85	$47.90
Purchase #5	$230.90	8.421%	$250.3441	$250.34	$250.35	$250.30
Purchase #6	$54.55	5.691%	$57.6544	$57.65	$57.65	$57.70
Purchase #7	$72.28	8.444%	$78.3833	$78.38	$78.40	$78.40
7 purchase totals =	$695.45		$765.4101	$765.40	$765.45	$765.40