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	$234.95	8.493%	$254.9043	$254.90	$254.90	$254.90
Purchase #2	$80.26	7.339%	$86.1503	$86.15	$86.15	$86.20
Purchase #3	$39.62	5.553%	$41.8201	$41.82	$41.80	$41.80
Purchase #4	$173.49	6.411%	$184.6124	$184.61	$184.60	$184.60
Purchase #5	$86.93	3.399%	$89.8848	$89.88	$89.90	$89.90
Purchase #6	$47.52	10.678%	$52.5942	$52.59	$52.60	$52.60
Purchase #7	$232.27	7.756%	$250.2849	$250.28	$250.30	$250.30
7 purchase totals =	$895.04		$960.2510	$960.23	$960.25	$960.30