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	$41.95	4.237%	$43.7274	$43.73	$43.75	$43.70
Purchase #2	$188.29	9.700%	$206.5541	$206.55	$206.55	$206.60
Purchase #3	$233.82	9.147%	$255.2075	$255.21	$255.20	$255.20
Purchase #4	$39.66	9.723%	$43.5161	$43.52	$43.50	$43.50
Purchase #5	$90.90	11.741%	$101.5726	$101.57	$101.55	$101.60
Purchase #6	$244.84	7.672%	$263.6241	$263.62	$263.60	$263.60
Purchase #7	$99.25	4.511%	$103.7272	$103.73	$103.75	$103.70
7 purchase totals =	$938.71		$1,017.9290	$1,017.93	$1,017.90	$1,017.90