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	$229.34	10.798%	$254.1041	$254.10	$254.10	$254.10
Purchase #2	$45.75	12.547%	$51.4903	$51.49	$51.50	$51.50
Purchase #3	$241.40	9.670%	$264.7434	$264.74	$264.75	$264.70
Purchase #4	$167.83	11.102%	$186.4625	$186.46	$186.45	$186.50
Purchase #5	$55.46	7.340%	$59.5308	$59.53	$59.55	$59.50
Purchase #6	$6.38	10.297%	$7.0369	$7.04	$7.05	$7.00
Purchase #7	$147.25	7.750%	$158.6619	$158.66	$158.65	$158.70
7 purchase totals =	$893.41		$982.0299	$982.02	$982.05	$982.00