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	$185.88	11.164%	$206.6316	$206.63	$206.65	$206.60
Purchase #2	$108.72	8.662%	$118.1373	$118.14	$118.15	$118.10
Purchase #3	$77.87	12.310%	$87.4558	$87.46	$87.45	$87.50
Purchase #4	$250.86	4.764%	$262.811	$262.81	$262.80	$262.80
Purchase #5	$143.88	10.566%	$159.0824	$159.08	$159.10	$159.10
Purchase #6	$162.39	3.756%	$168.4894	$168.49	$168.50	$168.50
Purchase #7	$48.40	12.644%	$54.5197	$54.52	$54.50	$54.50
7 purchase totals =	$978.00		$1,057.1272	$1,057.13	$1,057.15	$1,057.10