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	$74.76	11.663%	$83.4793	$83.48	$83.50	$83.50
Purchase #2	$240.52	3.220%	$248.2647	$248.26	$248.25	$248.30
Purchase #3	$212.45	8.682%	$230.8949	$230.89	$230.90	$230.90
Purchase #4	$32.41	7.690%	$34.9023	$34.90	$34.90	$34.90
Purchase #5	$56.75	4.432%	$59.2652	$59.27	$59.25	$59.30
Purchase #6	$96.44	7.341%	$103.5197	$103.52	$103.50	$103.50
Purchase #7	$205.27	7.145%	$219.9365	$219.94	$219.95	$219.90
7 purchase totals =	$918.60		$980.2626	$980.26	$980.25	$980.30