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	$133.91	9.638%	$146.8162	$146.82	$146.80	$146.80
Purchase #2	$177.94	10.343%	$196.3443	$196.34	$196.35	$196.30
Purchase #3	$9.62	3.292%	$9.9367	$9.94	$9.95	$9.90
Purchase #4	$89.32	13.818%	$101.6622	$101.66	$101.65	$101.70
Purchase #5	$245.82	7.365%	$263.9246	$263.92	$263.90	$263.90
Purchase #6	$136.54	4.417%	$142.571	$142.57	$142.55	$142.60
Purchase #7	$229.73	11.682%	$256.5671	$256.57	$256.55	$256.60
7 purchase totals =	$1,022.88		$1,117.8221	$1,117.82	$1,117.75	$1,117.80