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	$229.94	5.446%	$242.4625	$242.46	$242.45	$242.50
Purchase #2	$82.87	9.585%	$90.8131	$90.81	$90.80	$90.80
Purchase #3	$153.26	11.297%	$170.5738	$170.57	$170.55	$170.60
Purchase #4	$73.89	3.639%	$76.5789	$76.58	$76.60	$76.60
Purchase #5	$23.43	3.662%	$24.288	$24.29	$24.30	$24.30
Purchase #6	$84.83	6.850%	$90.6409	$90.64	$90.65	$90.60
Purchase #7	$150.29	11.631%	$167.7702	$167.77	$167.75	$167.80
7 purchase totals =	$798.51		$863.1274	$863.12	$863.10	$863.20