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	$160.52	5.191%	$168.8526	$168.85	$168.85	$168.90
Purchase #2	$121.63	13.417%	$137.9491	$137.95	$137.95	$137.90
Purchase #3	$13.59	11.500%	$15.1529	$15.15	$15.15	$15.20
Purchase #4	$111.60	5.792%	$118.0639	$118.06	$118.05	$118.10
Purchase #5	$189.96	7.704%	$204.5945	$204.59	$204.60	$204.60
Purchase #6	$215.94	12.662%	$243.2823	$243.28	$243.30	$243.30
Purchase #7	$94.92	3.346%	$98.096	$98.10	$98.10	$98.10
7 purchase totals =	$908.16		$985.9913	$985.98	$986.00	$986.10