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	$157.52	6.401%	$167.6029	$167.60	$167.60	$167.60
Purchase #2	$154.68	10.732%	$171.2803	$171.28	$171.30	$171.30
Purchase #3	$40.83	5.230%	$42.9654	$42.97	$42.95	$43.00
Purchase #4	$193.58	8.681%	$210.3847	$210.38	$210.40	$210.40
Purchase #5	$78.36	10.781%	$86.808	$86.81	$86.80	$86.80
Purchase #6	$37.65	6.511%	$40.1014	$40.10	$40.10	$40.10
Purchase #7	$145.95	7.494%	$156.8875	$156.89	$156.90	$156.90
7 purchase totals =	$808.57		$876.0302	$876.03	$876.05	$876.10