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	$50.29	6.468%	$53.5428	$53.54	$53.55	$53.50
Purchase #2	$17.75	3.687%	$18.4044	$18.40	$18.40	$18.40
Purchase #3	$82.94	3.573%	$85.9034	$85.90	$85.90	$85.90
Purchase #4	$16.48	9.673%	$18.0741	$18.07	$18.05	$18.10
Purchase #5	$50.56	7.774%	$54.4905	$54.49	$54.50	$54.50
Purchase #6	$56.41	6.228%	$59.9232	$59.92	$59.90	$59.90
Purchase #7	$7.74	12.742%	$8.7262	$8.73	$8.75	$8.70
7 purchase totals =	$282.17		$299.0646	$299.05	$299.05	$299.00