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	$151.49	10.156%	$166.8753	$166.88	$166.90	$166.90
Purchase #2	$244.75	8.622%	$265.8523	$265.85	$265.85	$265.90
Purchase #3	$53.99	3.381%	$55.8154	$55.82	$55.80	$55.80
Purchase #4	$250.91	9.796%	$275.4891	$275.49	$275.50	$275.50
Purchase #5	$84.89	5.208%	$89.3111	$89.31	$89.30	$89.30
Purchase #6	$96.77	6.431%	$102.9933	$102.99	$103.00	$103.00
Purchase #7	$93.30	11.182%	$103.7328	$103.73	$103.75	$103.70
7 purchase totals =	$976.10		$1,060.0693	$1,060.07	$1,060.10	$1,060.10