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	$233.71	11.454%	$260.4791	$260.48	$260.50	$260.50
Purchase #2	$55.48	4.248%	$57.8368	$57.84	$57.85	$57.80
Purchase #3	$103.28	5.380%	$108.8365	$108.84	$108.85	$108.80
Purchase #4	$161.32	4.625%	$168.7811	$168.78	$168.80	$168.80
Purchase #5	$232.85	3.609%	$241.2536	$241.25	$241.25	$241.30
Purchase #6	$246.77	6.251%	$262.1956	$262.20	$262.20	$262.20
Purchase #7	$55.76	6.794%	$59.5483	$59.55	$59.55	$59.50
7 purchase totals =	$1,089.17		$1,158.9310	$1,158.94	$1,159.00	$1,158.90