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	$175.81	6.642%	$187.4873	$187.49	$187.50	$187.50
Purchase #2	$246.30	8.144%	$266.3587	$266.36	$266.35	$266.40
Purchase #3	$28.90	8.182%	$31.2646	$31.26	$31.25	$31.30
Purchase #4	$37.42	9.182%	$40.8559	$40.86	$40.85	$40.90
Purchase #5	$181.49	5.323%	$191.1507	$191.15	$191.15	$191.20
Purchase #6	$211.93	13.624%	$240.8033	$240.80	$240.80	$240.80
Purchase #7	$83.67	4.432%	$87.3783	$87.38	$87.40	$87.40
7 purchase totals =	$965.52		$1,045.2988	$1,045.30	$1,045.30	$1,045.50