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	$31.98	3.362%	$33.0552	$33.06	$33.05	$33.10
Purchase #2	$105.52	13.592%	$119.8623	$119.86	$119.85	$119.90
Purchase #3	$247.61	6.770%	$264.3732	$264.37	$264.35	$264.40
Purchase #4	$73.25	8.352%	$79.3678	$79.37	$79.35	$79.40
Purchase #5	$239.25	6.832%	$255.5956	$255.60	$255.60	$255.60
Purchase #6	$241.69	10.760%	$267.6958	$267.70	$267.70	$267.70
Purchase #7	$24.38	12.655%	$27.4653	$27.47	$27.45	$27.50
7 purchase totals =	$963.68		$1,047.4152	$1,047.43	$1,047.35	$1,047.60