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	$223.98	11.828%	$250.4724	$250.47	$250.45	$250.50
Purchase #2	$206.66	4.643%	$216.2552	$216.26	$216.25	$216.30
Purchase #3	$82.62	13.306%	$93.6134	$93.61	$93.60	$93.60
Purchase #4	$98.88	12.504%	$111.244	$111.24	$111.25	$111.20
Purchase #5	$110.92	4.589%	$116.0101	$116.01	$116.00	$116.00
Purchase #6	$40.54	11.591%	$45.239	$45.24	$45.25	$45.20
Purchase #7	$249.33	13.330%	$282.5657	$282.57	$282.55	$282.60
7 purchase totals =	$1,012.93		$1,115.3998	$1,115.40	$1,115.35	$1,115.40