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	$75.53	4.243%	$78.7347	$78.73	$78.75	$78.70
Purchase #2	$129.77	10.117%	$142.8988	$142.90	$142.90	$142.90
Purchase #3	$179.52	8.510%	$194.7972	$194.80	$194.80	$194.80
Purchase #4	$147.48	3.730%	$152.981	$152.98	$153.00	$153.00
Purchase #5	$209.45	12.190%	$234.982	$234.98	$235.00	$235.00
Purchase #6	$174.34	12.464%	$196.0697	$196.07	$196.05	$196.10
Purchase #7	$221.80	12.468%	$249.454	$249.45	$249.45	$249.50
7 purchase totals =	$1,137.89		$1,249.9174	$1,249.91	$1,249.95	$1,250.00