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	$111.97	10.357%	$123.5667	$123.57	$123.55	$123.60
Purchase #2	$161.40	7.354%	$173.2694	$173.27	$173.25	$173.30
Purchase #3	$95.73	5.700%	$101.1866	$101.19	$101.20	$101.20
Purchase #4	$46.76	13.469%	$53.0581	$53.06	$53.05	$53.10
Purchase #5	$122.93	6.742%	$131.2179	$131.22	$131.20	$131.20
Purchase #6	$25.47	7.679%	$27.4258	$27.43	$27.45	$27.40
Purchase #7	$38.62	5.258%	$40.6506	$40.65	$40.65	$40.70
7 purchase totals =	$602.88		$650.3751	$650.39	$650.35	$650.50