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	$42.78	8.528%	$46.4283	$46.43	$46.45	$46.40
Purchase #2	$88.33	3.632%	$91.5381	$91.54	$91.55	$91.50
Purchase #3	$193.68	9.817%	$212.6936	$212.69	$212.70	$212.70
Purchase #4	$125.68	11.740%	$140.4348	$140.43	$140.45	$140.40
Purchase #5	$95.96	8.752%	$104.3584	$104.36	$104.35	$104.40
Purchase #6	$202.56	10.314%	$223.452	$223.45	$223.45	$223.50
Purchase #7	$151.41	7.124%	$162.1964	$162.20	$162.20	$162.20
7 purchase totals =	$900.40		$981.1016	$981.10	$981.15	$981.10