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	$203.89	7.698%	$219.5855	$219.59	$219.60	$219.60
Purchase #2	$196.46	8.695%	$213.5422	$213.54	$213.55	$213.50
Purchase #3	$28.29	6.670%	$30.1769	$30.18	$30.20	$30.20
Purchase #4	$85.56	5.550%	$90.3086	$90.31	$90.30	$90.30
Purchase #5	$221.96	6.798%	$237.0488	$237.05	$237.05	$237.00
Purchase #6	$137.55	13.441%	$156.0381	$156.04	$156.05	$156.00
Purchase #7	$77.42	10.244%	$85.3509	$85.35	$85.35	$85.40
7 purchase totals =	$951.13		$1,032.0510	$1,032.06	$1,032.10	$1,032.00