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	$99.34	4.148%	$103.4606	$103.46	$103.45	$103.50
Purchase #2	$109.60	13.589%	$124.4935	$124.49	$124.50	$124.50
Purchase #3	$234.43	11.365%	$261.073	$261.07	$261.05	$261.10
Purchase #4	$55.33	5.455%	$58.3483	$58.35	$58.35	$58.30
Purchase #5	$210.51	13.316%	$238.5415	$238.54	$238.55	$238.50
Purchase #6	$21.69	3.776%	$22.509	$22.51	$22.50	$22.50
Purchase #7	$230.43	3.725%	$239.0135	$239.01	$239.00	$239.00
7 purchase totals =	$961.33		$1,047.4394	$1,047.43	$1,047.40	$1,047.40