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	$32.75	5.334%	$34.4969	$34.50	$34.50	$34.50
Purchase #2	$25.81	11.791%	$28.8533	$28.85	$28.85	$28.90
Purchase #3	$64.47	6.105%	$68.4059	$68.41	$68.40	$68.40
Purchase #4	$211.75	10.783%	$234.583	$234.58	$234.60	$234.60
Purchase #5	$168.76	10.162%	$185.9094	$185.91	$185.90	$185.90
Purchase #6	$199.88	8.116%	$216.1023	$216.10	$216.10	$216.10
Purchase #7	$229.92	8.760%	$250.061	$250.06	$250.05	$250.10
7 purchase totals =	$933.34		$1,018.4118	$1,018.41	$1,018.40	$1,018.50