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	$155.33	10.658%	$171.8851	$171.89	$171.90	$171.90
Purchase #2	$90.52	3.201%	$93.4175	$93.42	$93.40	$93.40
Purchase #3	$205.25	5.563%	$216.6681	$216.67	$216.65	$216.70
Purchase #4	$191.49	10.169%	$210.9626	$210.96	$210.95	$211.00
Purchase #5	$148.39	13.262%	$168.0695	$168.07	$168.05	$168.10
Purchase #6	$158.34	9.305%	$173.0735	$173.07	$173.05	$173.10
Purchase #7	$73.74	4.524%	$77.076	$77.08	$77.10	$77.10
7 purchase totals =	$1,023.06		$1,111.1523	$1,111.16	$1,111.10	$1,111.30