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	$107.28	9.624%	$117.6046	$117.60	$117.60	$117.60
Purchase #2	$170.25	11.852%	$190.428	$190.43	$190.45	$190.40
Purchase #3	$37.74	11.529%	$42.091	$42.09	$42.10	$42.10
Purchase #4	$73.97	6.534%	$78.8032	$78.80	$78.80	$78.80
Purchase #5	$240.91	7.642%	$259.3203	$259.32	$259.30	$259.30
Purchase #6	$123.42	4.415%	$128.869	$128.87	$128.85	$128.90
Purchase #7	$220.63	11.293%	$245.5457	$245.55	$245.55	$245.50
7 purchase totals =	$974.20		$1,062.6618	$1,062.66	$1,062.65	$1,062.60