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	$168.73	13.280%	$191.1373	$191.14	$191.15	$191.10
Purchase #2	$57.83	7.862%	$62.3766	$62.38	$62.40	$62.40
Purchase #3	$94.54	4.286%	$98.592	$98.59	$98.60	$98.60
Purchase #4	$227.41	11.713%	$254.0465	$254.05	$254.05	$254.00
Purchase #5	$132.30	13.785%	$150.5376	$150.54	$150.55	$150.50
Purchase #6	$12.99	8.598%	$14.1069	$14.11	$14.10	$14.10
Purchase #7	$86.57	12.417%	$97.3194	$97.32	$97.30	$97.30
7 purchase totals =	$780.37		$868.1163	$868.13	$868.15	$868.00