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	$141.26	5.780%	$149.4248	$149.42	$149.40	$149.40
Purchase #2	$134.99	13.589%	$153.3338	$153.33	$153.35	$153.30
Purchase #3	$66.54	8.219%	$72.0089	$72.01	$72.00	$72.00
Purchase #4	$81.59	7.718%	$87.8871	$87.89	$87.90	$87.90
Purchase #5	$202.78	9.665%	$222.3787	$222.38	$222.40	$222.40
Purchase #6	$219.90	11.417%	$245.006	$245.01	$245.00	$245.00
Purchase #7	$147.66	7.601%	$158.8836	$158.88	$158.90	$158.90
7 purchase totals =	$994.72		$1,088.9229	$1,088.92	$1,088.95	$1,088.90