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	$42.91	7.260%	$46.0253	$46.03	$46.05	$46.00
Purchase #2	$31.46	13.231%	$35.6225	$35.62	$35.60	$35.60
Purchase #3	$192.60	9.450%	$210.8007	$210.80	$210.80	$210.80
Purchase #4	$130.98	11.234%	$145.6943	$145.69	$145.70	$145.70
Purchase #5	$63.69	13.754%	$72.4499	$72.45	$72.45	$72.40
Purchase #6	$98.95	5.827%	$104.7158	$104.72	$104.70	$104.70
Purchase #7	$157.89	13.644%	$179.4325	$179.43	$179.45	$179.40
7 purchase totals =	$718.48		$794.7410	$794.74	$794.75	$794.60