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	$142.74	13.674%	$162.2583	$162.26	$162.25	$162.30
Purchase #2	$119.90	9.835%	$131.6922	$131.69	$131.70	$131.70
Purchase #3	$199.76	5.332%	$210.4112	$210.41	$210.40	$210.40
Purchase #4	$68.71	4.194%	$71.5917	$71.59	$71.60	$71.60
Purchase #5	$233.73	11.613%	$260.8731	$260.87	$260.85	$260.90
Purchase #6	$17.95	9.382%	$19.6341	$19.63	$19.65	$19.60
Purchase #7	$218.71	13.713%	$248.7017	$248.70	$248.70	$248.70
7 purchase totals =	$1,001.50		$1,105.1623	$1,105.15	$1,105.15	$1,105.20