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	$64.66	12.680%	$72.8589	$72.86	$72.85	$72.90
Purchase #2	$161.27	9.199%	$176.1052	$176.11	$176.10	$176.10
Purchase #3	$172.83	11.359%	$192.4618	$192.46	$192.45	$192.50
Purchase #4	$157.95	6.170%	$167.6955	$167.70	$167.70	$167.70
Purchase #5	$119.59	6.548%	$127.4208	$127.42	$127.40	$127.40
Purchase #6	$43.77	4.548%	$45.7607	$45.76	$45.75	$45.80
Purchase #7	$56.92	12.132%	$63.8255	$63.83	$63.85	$63.80
7 purchase totals =	$776.99		$846.1284	$846.14	$846.10	$846.20