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	$150.80	3.614%	$156.2499	$156.25	$156.25	$156.20
Purchase #2	$75.38	4.512%	$78.7811	$78.78	$78.80	$78.80
Purchase #3	$210.81	8.660%	$229.0661	$229.07	$229.05	$229.10
Purchase #4	$130.82	4.665%	$136.9228	$136.92	$136.90	$136.90
Purchase #5	$64.61	3.719%	$67.0128	$67.01	$67.00	$67.00
Purchase #6	$105.57	3.185%	$108.9324	$108.93	$108.95	$108.90
Purchase #7	$211.91	13.680%	$240.8993	$240.90	$240.90	$240.90
7 purchase totals =	$949.90		$1,017.8644	$1,017.86	$1,017.85	$1,017.80