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	$41.74	11.730%	$46.6361	$46.64	$46.65	$46.60
Purchase #2	$54.41	9.222%	$59.4277	$59.43	$59.45	$59.40
Purchase #3	$195.89	11.725%	$218.8581	$218.86	$218.85	$218.90
Purchase #4	$90.62	12.823%	$102.2402	$102.24	$102.25	$102.20
Purchase #5	$61.96	4.288%	$64.6168	$64.62	$64.60	$64.60
Purchase #6	$195.56	5.374%	$206.0694	$206.07	$206.05	$206.10
Purchase #7	$75.35	9.724%	$82.677	$82.68	$82.70	$82.70
7 purchase totals =	$715.53		$780.5253	$780.54	$780.55	$780.50