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	$194.46	8.411%	$210.816	$210.82	$210.80	$210.80
Purchase #2	$26.98	7.139%	$28.9061	$28.91	$28.90	$28.90
Purchase #3	$172.61	10.187%	$190.1938	$190.19	$190.20	$190.20
Purchase #4	$211.44	5.297%	$222.64	$222.64	$222.65	$222.60
Purchase #5	$29.55	11.518%	$32.9536	$32.95	$32.95	$33.00
Purchase #6	$153.79	8.156%	$166.3331	$166.33	$166.35	$166.30
Purchase #7	$210.60	6.609%	$224.5186	$224.52	$224.50	$224.50
7 purchase totals =	$999.43		$1,076.3612	$1,076.36	$1,076.35	$1,076.30