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	$186.96	12.778%	$210.8497	$210.85	$210.85	$210.80
Purchase #2	$192.66	3.463%	$199.3318	$199.33	$199.35	$199.30
Purchase #3	$49.43	8.456%	$53.6098	$53.61	$53.60	$53.60
Purchase #4	$153.28	7.847%	$165.3079	$165.31	$165.30	$165.30
Purchase #5	$59.55	3.828%	$61.8296	$61.83	$61.85	$61.80
Purchase #6	$140.47	6.128%	$149.078	$149.08	$149.10	$149.10
Purchase #7	$42.47	3.402%	$43.9148	$43.91	$43.90	$43.90
7 purchase totals =	$824.82		$883.9216	$883.92	$883.95	$883.80