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	$173.46	8.230%	$187.7358	$187.74	$187.75	$187.70
Purchase #2	$145.95	11.358%	$162.527	$162.53	$162.55	$162.50
Purchase #3	$39.83	12.774%	$44.9179	$44.92	$44.90	$44.90
Purchase #4	$24.46	4.247%	$25.4988	$25.50	$25.50	$25.50
Purchase #5	$44.28	3.132%	$45.6668	$45.67	$45.65	$45.70
Purchase #6	$249.55	5.191%	$262.5041	$262.50	$262.50	$262.50
Purchase #7	$248.47	12.116%	$278.5746	$278.57	$278.55	$278.60
7 purchase totals =	$926.00		$1,007.4250	$1,007.43	$1,007.40	$1,007.40