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	$79.88	10.851%	$88.5478	$88.55	$88.55	$88.50
Purchase #2	$95.54	5.111%	$100.423	$100.42	$100.40	$100.40
Purchase #3	$222.73	12.354%	$250.2461	$250.25	$250.25	$250.20
Purchase #4	$151.92	13.441%	$172.3396	$172.34	$172.35	$172.30
Purchase #5	$75.40	8.839%	$82.0646	$82.06	$82.05	$82.10
Purchase #6	$192.49	7.445%	$206.8209	$206.82	$206.80	$206.80
Purchase #7	$230.92	3.309%	$238.5611	$238.56	$238.55	$238.60
7 purchase totals =	$1,048.88		$1,139.0031	$1,139.00	$1,138.95	$1,138.90