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	$156.91	9.667%	$172.0785	$172.08	$172.10	$172.10
Purchase #2	$23.28	13.789%	$26.4901	$26.49	$26.50	$26.50
Purchase #3	$35.96	4.358%	$37.5271	$37.53	$37.55	$37.50
Purchase #4	$87.71	12.343%	$98.536	$98.54	$98.55	$98.50
Purchase #5	$85.32	4.710%	$89.3386	$89.34	$89.35	$89.30
Purchase #6	$5.62	5.818%	$5.947	$5.95	$5.95	$5.90
Purchase #7	$244.83	9.369%	$267.7681	$267.77	$267.75	$267.80
7 purchase totals =	$639.63		$697.6854	$697.70	$697.75	$697.60