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	$86.97	8.374%	$94.2529	$94.25	$94.25	$94.30
Purchase #2	$33.93	11.654%	$37.8842	$37.88	$37.90	$37.90
Purchase #3	$99.84	9.683%	$109.5075	$109.51	$109.50	$109.50
Purchase #4	$63.47	5.410%	$66.9037	$66.90	$66.90	$66.90
Purchase #5	$134.98	13.676%	$153.4399	$153.44	$153.45	$153.40
Purchase #6	$209.72	4.134%	$218.3898	$218.39	$218.40	$218.40
Purchase #7	$212.52	4.237%	$221.5245	$221.52	$221.50	$221.50
7 purchase totals =	$841.43		$901.9025	$901.89	$901.90	$901.90