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	$70.59	12.583%	$79.4723	$79.47	$79.45	$79.50
Purchase #2	$7.56	12.151%	$8.4786	$8.48	$8.50	$8.50
Purchase #3	$60.39	11.375%	$67.2594	$67.26	$67.25	$67.30
Purchase #4	$73.74	11.642%	$82.3248	$82.32	$82.30	$82.30
Purchase #5	$45.89	9.656%	$50.3211	$50.32	$50.30	$50.30
Purchase #6	$201.46	11.279%	$224.1827	$224.18	$224.20	$224.20
Purchase #7	$185.67	10.871%	$205.8542	$205.85	$205.85	$205.90
7 purchase totals =	$645.30		$717.8931	$717.88	$717.85	$718.00