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	$162.31	9.855%	$178.3057	$178.31	$178.30	$178.30
Purchase #2	$33.90	3.302%	$35.0194	$35.02	$35.00	$35.00
Purchase #3	$90.56	13.598%	$102.8743	$102.87	$102.85	$102.90
Purchase #4	$191.93	11.736%	$214.4549	$214.45	$214.45	$214.50
Purchase #5	$197.94	4.197%	$206.2475	$206.25	$206.25	$206.20
Purchase #6	$127.73	7.604%	$137.4426	$137.44	$137.45	$137.40
Purchase #7	$160.64	6.754%	$171.4896	$171.49	$171.50	$171.50
7 purchase totals =	$965.01		$1,045.8340	$1,045.83	$1,045.80	$1,045.80