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	$49.58	5.448%	$52.2811	$52.28	$52.30	$52.30
Purchase #2	$76.76	6.141%	$81.4738	$81.47	$81.45	$81.50
Purchase #3	$127.60	4.665%	$133.5525	$133.55	$133.55	$133.60
Purchase #4	$63.96	12.520%	$71.9678	$71.97	$71.95	$72.00
Purchase #5	$233.93	7.131%	$250.6115	$250.61	$250.60	$250.60
Purchase #6	$99.43	13.579%	$112.9316	$112.93	$112.95	$112.90
Purchase #7	$144.41	12.248%	$162.0973	$162.10	$162.10	$162.10
7 purchase totals =	$795.67		$864.9156	$864.91	$864.90	$865.00