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	$67.26	5.356%	$70.8624	$70.86	$70.85	$70.90
Purchase #2	$204.85	8.551%	$222.3667	$222.37	$222.35	$222.40
Purchase #3	$199.48	11.454%	$222.3284	$222.33	$222.35	$222.30
Purchase #4	$129.27	13.121%	$146.2315	$146.23	$146.25	$146.20
Purchase #5	$224.30	9.437%	$245.4672	$245.47	$245.45	$245.50
Purchase #6	$146.40	12.406%	$164.5624	$164.56	$164.55	$164.60
Purchase #7	$106.86	6.500%	$113.8059	$113.81	$113.80	$113.80
7 purchase totals =	$1,078.42		$1,185.6245	$1,185.63	$1,185.60	$1,185.70