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	$219.28	11.132%	$243.6902	$243.69	$243.70	$243.70
Purchase #2	$112.91	13.256%	$127.8773	$127.88	$127.90	$127.90
Purchase #3	$73.78	3.125%	$76.0856	$76.09	$76.10	$76.10
Purchase #4	$176.25	5.272%	$185.5419	$185.54	$185.55	$185.50
Purchase #5	$54.88	3.581%	$56.8453	$56.85	$56.85	$56.80
Purchase #6	$109.43	10.501%	$120.9212	$120.92	$120.90	$120.90
Purchase #7	$93.56	5.844%	$99.0276	$99.03	$99.05	$99.00
7 purchase totals =	$840.09		$909.9891	$910.00	$910.05	$909.90