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	$181.63	7.279%	$194.8508	$194.85	$194.85	$194.90
Purchase #2	$147.69	6.281%	$156.9664	$156.97	$156.95	$157.00
Purchase #3	$54.28	4.201%	$56.5603	$56.56	$56.55	$56.60
Purchase #4	$179.57	11.852%	$200.8526	$200.85	$200.85	$200.90
Purchase #5	$183.86	3.805%	$190.8559	$190.86	$190.85	$190.90
Purchase #6	$51.83	5.317%	$54.5858	$54.59	$54.60	$54.60
Purchase #7	$60.74	11.776%	$67.8927	$67.89	$67.90	$67.90
7 purchase totals =	$859.60		$922.5645	$922.57	$922.55	$922.80