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	$181.38	10.650%	$200.697	$200.70	$200.70	$200.70
Purchase #2	$163.93	3.401%	$169.5053	$169.51	$169.50	$169.50
Purchase #3	$124.35	11.675%	$138.8679	$138.87	$138.85	$138.90
Purchase #4	$134.33	9.357%	$146.8993	$146.90	$146.90	$146.90
Purchase #5	$223.41	8.620%	$242.6679	$242.67	$242.65	$242.70
Purchase #6	$45.83	13.715%	$52.1156	$52.12	$52.10	$52.10
Purchase #7	$96.52	3.180%	$99.5893	$99.59	$99.60	$99.60
7 purchase totals =	$969.75		$1,050.3423	$1,050.36	$1,050.30	$1,050.40