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	$229.94	10.365%	$253.7733	$253.77	$253.75	$253.80
Purchase #2	$30.71	3.138%	$31.6737	$31.67	$31.65	$31.70
Purchase #3	$229.78	13.836%	$261.5724	$261.57	$261.55	$261.60
Purchase #4	$125.90	8.594%	$136.7198	$136.72	$136.70	$136.70
Purchase #5	$55.64	6.773%	$59.4085	$59.41	$59.40	$59.40
Purchase #6	$40.91	9.782%	$44.9118	$44.91	$44.90	$44.90
Purchase #7	$180.59	13.719%	$205.3651	$205.37	$205.35	$205.40
7 purchase totals =	$893.47		$993.4246	$993.42	$993.30	$993.50