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	$232.73	11.708%	$259.978	$259.98	$260.00	$260.00
Purchase #2	$78.74	4.206%	$82.0518	$82.05	$82.05	$82.10
Purchase #3	$53.42	5.281%	$56.2411	$56.24	$56.25	$56.20
Purchase #4	$241.68	10.845%	$267.8902	$267.89	$267.90	$267.90
Purchase #5	$33.41	12.327%	$37.5285	$37.53	$37.55	$37.50
Purchase #6	$162.95	7.407%	$175.0197	$175.02	$175.00	$175.00
Purchase #7	$159.50	5.839%	$168.8132	$168.81	$168.80	$168.80
7 purchase totals =	$962.43		$1,047.5225	$1,047.52	$1,047.55	$1,047.50