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	$110.40	8.111%	$119.3545	$119.35	$119.35	$119.40
Purchase #2	$43.76	4.629%	$45.7857	$45.79	$45.80	$45.80
Purchase #3	$93.88	13.456%	$106.5125	$106.51	$106.50	$106.50
Purchase #4	$188.32	13.553%	$213.843	$213.84	$213.85	$213.80
Purchase #5	$184.38	3.807%	$191.3993	$191.40	$191.40	$191.40
Purchase #6	$173.66	9.594%	$190.3209	$190.32	$190.30	$190.30
Purchase #7	$143.47	7.498%	$154.2274	$154.23	$154.25	$154.20
7 purchase totals =	$937.87		$1,021.4433	$1,021.44	$1,021.45	$1,021.40