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	$162.83	10.324%	$179.6406	$179.64	$179.65	$179.60
Purchase #2	$100.97	12.500%	$113.5913	$113.59	$113.60	$113.60
Purchase #3	$209.66	4.121%	$218.3001	$218.30	$218.30	$218.30
Purchase #4	$175.48	12.154%	$196.8078	$196.81	$196.80	$196.80
Purchase #5	$224.76	6.144%	$238.5693	$238.57	$238.55	$238.60
Purchase #6	$94.46	6.690%	$100.7794	$100.78	$100.80	$100.80
Purchase #7	$57.66	4.409%	$60.2022	$60.20	$60.20	$60.20
7 purchase totals =	$1,025.82		$1,107.8907	$1,107.89	$1,107.90	$1,107.90