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	$34.89	10.213%	$38.4533	$38.45	$38.45	$38.50
Purchase #2	$12.96	12.651%	$14.5996	$14.60	$14.60	$14.60
Purchase #3	$167.36	12.495%	$188.2716	$188.27	$188.25	$188.30
Purchase #4	$162.33	6.769%	$173.3181	$173.32	$173.30	$173.30
Purchase #5	$188.53	8.455%	$204.4702	$204.47	$204.45	$204.50
Purchase #6	$36.42	12.360%	$40.9215	$40.92	$40.90	$40.90
Purchase #7	$127.46	9.392%	$139.431	$139.43	$139.45	$139.40
7 purchase totals =	$729.95		$799.4653	$799.46	$799.40	$799.50