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	$117.35	5.213%	$123.4675	$123.47	$123.45	$123.50
Purchase #2	$114.62	4.460%	$119.7321	$119.73	$119.75	$119.70
Purchase #3	$134.90	9.252%	$147.3809	$147.38	$147.40	$147.40
Purchase #4	$146.27	9.705%	$160.4655	$160.47	$160.45	$160.50
Purchase #5	$210.52	5.430%	$221.9512	$221.95	$221.95	$222.00
Purchase #6	$170.76	4.513%	$178.4664	$178.47	$178.45	$178.50
Purchase #7	$77.66	10.619%	$85.9067	$85.91	$85.90	$85.90
7 purchase totals =	$972.08		$1,037.3703	$1,037.38	$1,037.35	$1,037.50