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	$174.74	8.500%	$189.5929	$189.59	$189.60	$189.60
Purchase #2	$160.66	11.775%	$179.5777	$179.58	$179.60	$179.60
Purchase #3	$41.77	12.642%	$47.0506	$47.05	$47.05	$47.10
Purchase #4	$64.32	9.406%	$70.3699	$70.37	$70.35	$70.40
Purchase #5	$78.32	8.724%	$85.1526	$85.15	$85.15	$85.20
Purchase #6	$36.71	9.801%	$40.3079	$40.31	$40.30	$40.30
Purchase #7	$85.55	7.177%	$91.6899	$91.69	$91.70	$91.70
7 purchase totals =	$642.07		$703.7415	$703.74	$703.75	$703.90