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	$129.91	7.675%	$139.8806	$139.88	$139.90	$139.90
Purchase #2	$99.25	7.761%	$106.9528	$106.95	$106.95	$107.00
Purchase #3	$178.27	7.772%	$192.1251	$192.13	$192.15	$192.10
Purchase #4	$51.64	7.222%	$55.3694	$55.37	$55.35	$55.40
Purchase #5	$215.36	12.166%	$241.5607	$241.56	$241.55	$241.60
Purchase #6	$158.50	6.522%	$168.8374	$168.84	$168.85	$168.80
Purchase #7	$160.55	3.608%	$166.3426	$166.34	$166.35	$166.30
7 purchase totals =	$993.48		$1,071.0686	$1,071.07	$1,071.10	$1,071.10