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	$125.75	4.753%	$131.7269	$131.73	$131.75	$131.70
Purchase #2	$107.31	6.157%	$113.9171	$113.92	$113.90	$113.90
Purchase #3	$163.33	3.630%	$169.2589	$169.26	$169.25	$169.30
Purchase #4	$41.36	9.403%	$45.2491	$45.25	$45.25	$45.20
Purchase #5	$28.34	10.792%	$31.3985	$31.40	$31.40	$31.40
Purchase #6	$241.28	3.861%	$250.5958	$250.60	$250.60	$250.60
Purchase #7	$40.80	5.662%	$43.1101	$43.11	$43.10	$43.10
7 purchase totals =	$748.17		$785.2564	$785.27	$785.25	$785.20