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	$41.91	4.130%	$43.6409	$43.64	$43.65	$43.60
Purchase #2	$210.75	12.569%	$237.2392	$237.24	$237.25	$237.20
Purchase #3	$72.93	7.146%	$78.1416	$78.14	$78.15	$78.10
Purchase #4	$88.45	4.710%	$92.616	$92.62	$92.60	$92.60
Purchase #5	$38.28	9.425%	$41.8879	$41.89	$41.90	$41.90
Purchase #6	$40.76	3.645%	$42.2457	$42.25	$42.25	$42.20
Purchase #7	$9.50	10.524%	$10.4998	$10.50	$10.50	$10.50
7 purchase totals =	$502.58		$546.2711	$546.28	$546.30	$546.10