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	$169.25	10.471%	$186.9722	$186.97	$186.95	$187.00
Purchase #2	$72.66	3.810%	$75.4283	$75.43	$75.45	$75.40
Purchase #3	$179.60	7.143%	$192.4288	$192.43	$192.45	$192.40
Purchase #4	$52.48	13.144%	$59.378	$59.38	$59.40	$59.40
Purchase #5	$235.72	6.611%	$251.3034	$251.30	$251.30	$251.30
Purchase #6	$235.55	5.430%	$248.3404	$248.34	$248.35	$248.30
Purchase #7	$150.94	11.610%	$168.4641	$168.46	$168.45	$168.50
7 purchase totals =	$1,096.20		$1,182.3152	$1,182.31	$1,182.35	$1,182.30