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	$82.80	11.707%	$92.4934	$92.49	$92.50	$92.50
Purchase #2	$78.91	4.529%	$82.4838	$82.48	$82.50	$82.50
Purchase #3	$41.30	3.664%	$42.8132	$42.81	$42.80	$42.80
Purchase #4	$193.56	9.212%	$211.3907	$211.39	$211.40	$211.40
Purchase #5	$219.92	4.531%	$229.8846	$229.88	$229.90	$229.90
Purchase #6	$115.41	9.232%	$126.0647	$126.06	$126.05	$126.10
Purchase #7	$77.37	12.824%	$87.2919	$87.29	$87.30	$87.30
7 purchase totals =	$809.27		$872.4223	$872.40	$872.45	$872.50