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	$152.30	9.752%	$167.1523	$167.15	$167.15	$167.20
Purchase #2	$179.93	7.162%	$192.8166	$192.82	$192.80	$192.80
Purchase #3	$60.97	7.523%	$65.5568	$65.56	$65.55	$65.60
Purchase #4	$250.80	7.440%	$269.4595	$269.46	$269.45	$269.50
Purchase #5	$195.89	10.850%	$217.1441	$217.14	$217.15	$217.10
Purchase #6	$12.49	8.242%	$13.5194	$13.52	$13.50	$13.50
Purchase #7	$86.53	10.586%	$95.6901	$95.69	$95.70	$95.70
7 purchase totals =	$938.91		$1,021.3388	$1,021.34	$1,021.30	$1,021.40