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	$133.46	6.800%	$142.5353	$142.54	$142.55	$142.50
Purchase #2	$37.45	8.688%	$40.7037	$40.70	$40.70	$40.70
Purchase #3	$66.62	11.385%	$74.2047	$74.20	$74.20	$74.20
Purchase #4	$158.62	4.822%	$166.2687	$166.27	$166.25	$166.30
Purchase #5	$182.76	4.831%	$191.5891	$191.59	$191.60	$191.60
Purchase #6	$59.58	13.638%	$67.7055	$67.71	$67.70	$67.70
Purchase #7	$143.53	13.380%	$162.7343	$162.73	$162.75	$162.70
7 purchase totals =	$782.02		$845.7413	$845.74	$845.75	$845.70