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	$200.89	7.315%	$215.5851	$215.59	$215.60	$215.60
Purchase #2	$10.56	13.874%	$12.0251	$12.03	$12.05	$12.00
Purchase #3	$53.74	5.700%	$56.8032	$56.80	$56.80	$56.80
Purchase #4	$53.49	6.408%	$56.9176	$56.92	$56.90	$56.90
Purchase #5	$167.72	7.460%	$180.2319	$180.23	$180.25	$180.20
Purchase #6	$99.85	12.645%	$112.476	$112.48	$112.50	$112.50
Purchase #7	$143.60	3.346%	$148.4049	$148.40	$148.40	$148.40
7 purchase totals =	$729.85		$782.4438	$782.45	$782.50	$782.40