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	$94.71	5.304%	$99.7334	$99.73	$99.75	$99.70
Purchase #2	$165.59	11.598%	$184.7951	$184.80	$184.80	$184.80
Purchase #3	$241.95	6.710%	$258.1848	$258.18	$258.20	$258.20
Purchase #4	$244.95	6.113%	$259.9238	$259.92	$259.90	$259.90
Purchase #5	$167.40	13.799%	$190.4995	$190.50	$190.50	$190.50
Purchase #6	$9.51	10.471%	$10.5058	$10.51	$10.50	$10.50
Purchase #7	$156.48	5.389%	$164.9127	$164.91	$164.90	$164.90
7 purchase totals =	$1,080.59		$1,168.5551	$1,168.55	$1,168.55	$1,168.50