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	$28.52	13.626%	$32.4061	$32.41	$32.40	$32.40
Purchase #2	$113.38	11.665%	$126.6058	$126.61	$126.60	$126.60
Purchase #3	$67.96	7.288%	$72.9129	$72.91	$72.90	$72.90
Purchase #4	$99.29	13.525%	$112.719	$112.72	$112.70	$112.70
Purchase #5	$202.31	6.157%	$214.7662	$214.77	$214.75	$214.80
Purchase #6	$5.57	13.102%	$6.2998	$6.30	$6.30	$6.30
Purchase #7	$142.45	12.544%	$160.3189	$160.32	$160.30	$160.30
7 purchase totals =	$659.48		$726.0287	$726.04	$725.95	$726.00