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	$196.46	8.299%	$212.7642	$212.76	$212.75	$212.80
Purchase #2	$126.99	3.542%	$131.488	$131.49	$131.50	$131.50
Purchase #3	$24.96	3.695%	$25.8823	$25.88	$25.90	$25.90
Purchase #4	$178.52	7.416%	$191.759	$191.76	$191.75	$191.80
Purchase #5	$82.89	7.641%	$89.2236	$89.22	$89.20	$89.20
Purchase #6	$139.84	10.274%	$154.2072	$154.21	$154.20	$154.20
Purchase #7	$26.85	7.612%	$28.8938	$28.89	$28.90	$28.90
7 purchase totals =	$776.51		$834.2181	$834.21	$834.20	$834.30