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	$122.34	7.308%	$131.2806	$131.28	$131.30	$131.30
Purchase #2	$6.97	6.663%	$7.4344	$7.43	$7.45	$7.40
Purchase #3	$134.56	13.199%	$152.3206	$152.32	$152.30	$152.30
Purchase #4	$168.50	11.788%	$188.3628	$188.36	$188.35	$188.40
Purchase #5	$108.29	7.147%	$116.0295	$116.03	$116.05	$116.00
Purchase #6	$65.73	7.524%	$70.6755	$70.68	$70.70	$70.70
Purchase #7	$38.89	6.669%	$41.4836	$41.48	$41.50	$41.50
7 purchase totals =	$645.28		$707.5870	$707.58	$707.65	$707.60