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	$223.59	11.147%	$248.5136	$248.51	$248.50	$248.50
Purchase #2	$26.94	13.271%	$30.5152	$30.52	$30.50	$30.50
Purchase #3	$13.42	3.469%	$13.8855	$13.89	$13.90	$13.90
Purchase #4	$108.46	3.613%	$112.3787	$112.38	$112.40	$112.40
Purchase #5	$238.91	13.719%	$271.6861	$271.69	$271.70	$271.70
Purchase #6	$122.40	3.794%	$127.0439	$127.04	$127.05	$127.00
Purchase #7	$73.46	12.819%	$82.8768	$82.88	$82.90	$82.90
7 purchase totals =	$807.18		$886.8998	$886.91	$886.95	$886.90