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	$98.78	6.155%	$104.8599	$104.86	$104.85	$104.90
Purchase #2	$100.56	6.766%	$107.3639	$107.36	$107.35	$107.40
Purchase #3	$41.35	9.639%	$45.3357	$45.34	$45.35	$45.30
Purchase #4	$179.26	6.334%	$190.6143	$190.61	$190.60	$190.60
Purchase #5	$40.46	8.519%	$43.9068	$43.91	$43.90	$43.90
Purchase #6	$224.60	11.486%	$250.3976	$250.40	$250.40	$250.40
Purchase #7	$189.81	3.234%	$195.9485	$195.95	$195.95	$195.90
7 purchase totals =	$874.82		$938.4267	$938.43	$938.40	$938.40