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	$40.40	7.263%	$43.3343	$43.33	$43.35	$43.30
Purchase #2	$227.88	12.180%	$255.6358	$255.64	$255.65	$255.60
Purchase #3	$31.92	6.215%	$33.9038	$33.90	$33.90	$33.90
Purchase #4	$228.50	6.139%	$242.5276	$242.53	$242.55	$242.50
Purchase #5	$183.67	6.648%	$195.8804	$195.88	$195.90	$195.90
Purchase #6	$104.89	4.373%	$109.4768	$109.48	$109.50	$109.50
Purchase #7	$168.68	12.668%	$190.0484	$190.05	$190.05	$190.00
7 purchase totals =	$985.94		$1,070.8071	$1,070.81	$1,070.90	$1,070.70