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	$134.50	13.341%	$152.4436	$152.44	$152.45	$152.40
Purchase #2	$103.89	5.748%	$109.8616	$109.86	$109.85	$109.90
Purchase #3	$61.40	10.249%	$67.6929	$67.69	$67.70	$67.70
Purchase #4	$42.32	6.807%	$45.2007	$45.20	$45.20	$45.20
Purchase #5	$161.41	8.237%	$174.7053	$174.71	$174.70	$174.70
Purchase #6	$92.54	3.109%	$95.4171	$95.42	$95.40	$95.40
Purchase #7	$123.40	10.172%	$135.9522	$135.95	$135.95	$136.00
7 purchase totals =	$719.46		$781.2734	$781.27	$781.25	$781.30