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	$250.76	10.250%	$276.4629	$276.46	$276.45	$276.50
Purchase #2	$31.47	7.665%	$33.8822	$33.88	$33.90	$33.90
Purchase #3	$62.74	11.755%	$70.1151	$70.12	$70.10	$70.10
Purchase #4	$17.36	7.126%	$18.5971	$18.60	$18.60	$18.60
Purchase #5	$102.69	6.714%	$109.5846	$109.58	$109.60	$109.60
Purchase #6	$177.98	4.745%	$186.4252	$186.43	$186.45	$186.40
Purchase #7	$191.94	11.689%	$214.3759	$214.38	$214.40	$214.40
7 purchase totals =	$834.94		$909.4430	$909.45	$909.50	$909.50