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	$201.49	8.851%	$219.3239	$219.32	$219.30	$219.30
Purchase #2	$38.83	12.841%	$43.8162	$43.82	$43.80	$43.80
Purchase #3	$99.96	9.629%	$109.5851	$109.59	$109.60	$109.60
Purchase #4	$148.84	7.425%	$159.8914	$159.89	$159.90	$159.90
Purchase #5	$72.28	6.226%	$76.7802	$76.78	$76.80	$76.80
Purchase #6	$58.94	8.232%	$63.7919	$63.79	$63.80	$63.80
Purchase #7	$60.72	11.202%	$67.5219	$67.52	$67.50	$67.50
7 purchase totals =	$681.06		$740.7106	$740.71	$740.70	$740.70