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	$224.48	4.196%	$233.8992	$233.90	$233.90	$233.90
Purchase #2	$50.37	4.836%	$52.8059	$52.81	$52.80	$52.80
Purchase #3	$85.63	6.150%	$90.8962	$90.90	$90.90	$90.90
Purchase #4	$25.73	8.482%	$27.9124	$27.91	$27.90	$27.90
Purchase #5	$170.81	12.355%	$191.9136	$191.91	$191.90	$191.90
Purchase #6	$171.27	6.688%	$182.7245	$182.72	$182.70	$182.70
Purchase #7	$77.74	4.746%	$81.4295	$81.43	$81.45	$81.40
7 purchase totals =	$806.03		$861.5813	$861.58	$861.55	$861.50