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	$119.63	3.457%	$123.7656	$123.77	$123.75	$123.80
Purchase #2	$152.87	13.284%	$173.1773	$173.18	$173.20	$173.20
Purchase #3	$240.72	11.520%	$268.4509	$268.45	$268.45	$268.50
Purchase #4	$227.95	3.626%	$236.2155	$236.22	$236.20	$236.20
Purchase #5	$149.60	10.362%	$165.1016	$165.10	$165.10	$165.10
Purchase #6	$103.36	13.119%	$116.9198	$116.92	$116.90	$116.90
Purchase #7	$72.50	5.429%	$76.436	$76.44	$76.45	$76.40
7 purchase totals =	$1,066.63		$1,160.0667	$1,160.08	$1,160.05	$1,160.10