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	$177.51	10.593%	$196.3136	$196.31	$196.30	$196.30
Purchase #2	$136.42	8.492%	$148.0048	$148.00	$148.00	$148.00
Purchase #3	$11.71	9.614%	$12.8358	$12.84	$12.85	$12.80
Purchase #4	$170.28	12.757%	$192.0026	$192.00	$192.00	$192.00
Purchase #5	$138.66	13.405%	$157.2474	$157.25	$157.25	$157.20
Purchase #6	$230.90	6.162%	$245.1281	$245.13	$245.15	$245.10
Purchase #7	$136.82	8.839%	$148.9135	$148.91	$148.90	$148.90
7 purchase totals =	$1,002.30		$1,100.4458	$1,100.44	$1,100.45	$1,100.30