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	$136.83	6.574%	$145.8252	$145.83	$145.85	$145.80
Purchase #2	$152.35	10.675%	$168.6134	$168.61	$168.60	$168.60
Purchase #3	$189.48	9.857%	$208.157	$208.16	$208.15	$208.20
Purchase #4	$169.34	11.450%	$188.7294	$188.73	$188.75	$188.70
Purchase #5	$127.28	7.537%	$136.8731	$136.87	$136.85	$136.90
Purchase #6	$42.32	3.853%	$43.9506	$43.95	$43.95	$44.00
Purchase #7	$159.74	5.332%	$168.2573	$168.26	$168.25	$168.30
7 purchase totals =	$977.34		$1,060.4060	$1,060.41	$1,060.40	$1,060.50