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	$162.78	9.500%	$178.2441	$178.24	$178.25	$178.20
Purchase #2	$168.34	6.239%	$178.8427	$178.84	$178.85	$178.80
Purchase #3	$26.73	5.315%	$28.1507	$28.15	$28.15	$28.20
Purchase #4	$184.95	6.258%	$196.5242	$196.52	$196.50	$196.50
Purchase #5	$180.50	13.604%	$205.0552	$205.06	$205.05	$205.10
Purchase #6	$73.96	7.437%	$79.4604	$79.46	$79.45	$79.50
Purchase #7	$84.80	13.648%	$96.3735	$96.37	$96.35	$96.40
7 purchase totals =	$882.06		$962.6508	$962.64	$962.60	$962.70