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	$147.67	8.791%	$160.6517	$160.65	$160.65	$160.70
Purchase #2	$52.38	6.103%	$55.5768	$55.58	$55.60	$55.60
Purchase #3	$227.65	9.702%	$249.7366	$249.74	$249.75	$249.70
Purchase #4	$114.76	8.524%	$124.5421	$124.54	$124.55	$124.50
Purchase #5	$231.41	10.427%	$255.5391	$255.54	$255.55	$255.50
Purchase #6	$55.96	11.202%	$62.2286	$62.23	$62.25	$62.20
Purchase #7	$40.56	3.827%	$42.1122	$42.11	$42.10	$42.10
7 purchase totals =	$870.39		$950.3871	$950.39	$950.45	$950.30