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	$73.43	11.130%	$81.6028	$81.60	$81.60	$81.60
Purchase #2	$143.31	13.637%	$162.8532	$162.85	$162.85	$162.90
Purchase #3	$48.56	3.254%	$50.1401	$50.14	$50.15	$50.10
Purchase #4	$171.47	6.624%	$182.8282	$182.83	$182.85	$182.80
Purchase #5	$112.87	12.835%	$127.3569	$127.36	$127.35	$127.40
Purchase #6	$149.83	3.231%	$154.671	$154.67	$154.65	$154.70
Purchase #7	$47.99	10.374%	$52.9685	$52.97	$52.95	$53.00
7 purchase totals =	$747.46		$812.4207	$812.42	$812.40	$812.50