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	$212.81	5.131%	$223.7293	$223.73	$223.75	$223.70
Purchase #2	$95.70	7.813%	$103.177	$103.18	$103.20	$103.20
Purchase #3	$55.92	11.334%	$62.258	$62.26	$62.25	$62.30
Purchase #4	$115.44	3.439%	$119.41	$119.41	$119.40	$119.40
Purchase #5	$29.93	8.280%	$32.4082	$32.41	$32.40	$32.40
Purchase #6	$31.53	4.614%	$32.9848	$32.98	$33.00	$33.00
Purchase #7	$164.51	6.312%	$174.8939	$174.89	$174.90	$174.90
7 purchase totals =	$705.84		$748.8612	$748.86	$748.90	$748.90