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	$86.77	8.863%	$94.4604	$94.46	$94.45	$94.50
Purchase #2	$218.98	10.637%	$242.2729	$242.27	$242.25	$242.30
Purchase #3	$203.76	8.746%	$221.5808	$221.58	$221.60	$221.60
Purchase #4	$176.53	8.569%	$191.6569	$191.66	$191.65	$191.70
Purchase #5	$39.82	6.501%	$42.4087	$42.41	$42.40	$42.40
Purchase #6	$149.62	4.280%	$156.0237	$156.02	$156.00	$156.00
Purchase #7	$128.52	11.405%	$143.1777	$143.18	$143.20	$143.20
7 purchase totals =	$1,004.00		$1,091.5811	$1,091.58	$1,091.55	$1,091.70