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	$104.82	4.677%	$109.7224	$109.72	$109.70	$109.70
Purchase #2	$94.38	6.869%	$100.863	$100.86	$100.85	$100.90
Purchase #3	$30.59	3.447%	$31.6444	$31.64	$31.65	$31.60
Purchase #4	$118.44	10.529%	$130.9105	$130.91	$130.90	$130.90
Purchase #5	$115.44	11.384%	$128.5817	$128.58	$128.60	$128.60
Purchase #6	$20.58	10.264%	$22.6923	$22.69	$22.70	$22.70
Purchase #7	$155.36	8.847%	$169.1047	$169.10	$169.10	$169.10
7 purchase totals =	$639.61		$693.5190	$693.50	$693.50	$693.50