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	$99.39	13.552%	$112.8593	$112.86	$112.85	$112.90
Purchase #2	$238.90	4.854%	$250.4962	$250.50	$250.50	$250.50
Purchase #3	$245.52	9.439%	$268.6946	$268.69	$268.70	$268.70
Purchase #4	$44.48	13.371%	$50.4274	$50.43	$50.45	$50.40
Purchase #5	$33.42	6.637%	$35.6381	$35.64	$35.65	$35.60
Purchase #6	$85.55	7.751%	$92.181	$92.18	$92.20	$92.20
Purchase #7	$176.53	7.697%	$190.1175	$190.12	$190.10	$190.10
7 purchase totals =	$923.79		$1,000.4141	$1,000.42	$1,000.45	$1,000.40