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	$120.69	5.859%	$127.7612	$127.76	$127.75	$127.80
Purchase #2	$87.40	4.635%	$91.451	$91.45	$91.45	$91.50
Purchase #3	$85.56	10.421%	$94.4762	$94.48	$94.50	$94.50
Purchase #4	$249.97	6.860%	$267.1179	$267.12	$267.10	$267.10
Purchase #5	$151.53	3.397%	$156.6775	$156.68	$156.70	$156.70
Purchase #6	$177.45	10.874%	$196.7459	$196.75	$196.75	$196.70
Purchase #7	$161.98	13.292%	$183.5104	$183.51	$183.50	$183.50
7 purchase totals =	$1,034.58		$1,117.7401	$1,117.75	$1,117.75	$1,117.80