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	$101.75	12.658%	$114.6295	$114.63	$114.65	$114.60
Purchase #2	$137.92	11.207%	$153.3767	$153.38	$153.40	$153.40
Purchase #3	$217.27	12.694%	$244.8503	$244.85	$244.85	$244.90
Purchase #4	$100.59	4.275%	$104.8902	$104.89	$104.90	$104.90
Purchase #5	$122.32	10.473%	$135.1306	$135.13	$135.15	$135.10
Purchase #6	$150.49	5.727%	$159.1086	$159.11	$159.10	$159.10
Purchase #7	$81.88	10.152%	$90.1925	$90.19	$90.20	$90.20
7 purchase totals =	$912.22		$1,002.1784	$1,002.18	$1,002.25	$1,002.20