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	$49.84	11.489%	$55.5661	$55.57	$55.55	$55.60
Purchase #2	$84.41	7.112%	$90.4132	$90.41	$90.40	$90.40
Purchase #3	$52.87	4.563%	$55.2825	$55.28	$55.30	$55.30
Purchase #4	$132.76	7.597%	$142.8458	$142.85	$142.85	$142.80
Purchase #5	$48.84	11.204%	$54.312	$54.31	$54.30	$54.30
Purchase #6	$155.81	12.852%	$175.8347	$175.83	$175.85	$175.80
Purchase #7	$198.90	4.206%	$207.2657	$207.27	$207.25	$207.30
7 purchase totals =	$723.43		$781.5200	$781.52	$781.50	$781.50