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	$226.58	10.813%	$251.0801	$251.08	$251.10	$251.10
Purchase #2	$83.94	11.502%	$93.5948	$93.59	$93.60	$93.60
Purchase #3	$31.75	5.238%	$33.4131	$33.41	$33.40	$33.40
Purchase #4	$214.44	3.283%	$221.4801	$221.48	$221.50	$221.50
Purchase #5	$97.92	12.250%	$109.9152	$109.92	$109.90	$109.90
Purchase #6	$57.50	3.269%	$59.3797	$59.38	$59.40	$59.40
Purchase #7	$115.54	11.293%	$128.5879	$128.59	$128.60	$128.60
7 purchase totals =	$827.67		$897.4509	$897.45	$897.50	$897.50