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	$103.82	5.444%	$109.472	$109.47	$109.45	$109.50
Purchase #2	$35.32	5.223%	$37.1648	$37.16	$37.15	$37.20
Purchase #3	$30.59	6.664%	$32.6285	$32.63	$32.65	$32.60
Purchase #4	$125.31	4.114%	$130.4653	$130.47	$130.45	$130.50
Purchase #5	$187.47	7.773%	$202.042	$202.04	$202.05	$202.00
Purchase #6	$177.36	11.543%	$197.8327	$197.83	$197.85	$197.80
Purchase #7	$77.64	11.393%	$86.4855	$86.49	$86.50	$86.50
7 purchase totals =	$737.51		$796.0908	$796.09	$796.10	$796.10