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	$167.34	3.772%	$173.6521	$173.65	$173.65	$173.70
Purchase #2	$233.96	4.777%	$245.1363	$245.14	$245.15	$245.10
Purchase #3	$244.53	7.545%	$262.9798	$262.98	$263.00	$263.00
Purchase #4	$143.26	5.234%	$150.7582	$150.76	$150.75	$150.80
Purchase #5	$47.58	10.534%	$52.5921	$52.59	$52.60	$52.60
Purchase #6	$183.55	8.740%	$199.5923	$199.59	$199.60	$199.60
Purchase #7	$84.31	6.874%	$90.1055	$90.11	$90.10	$90.10
7 purchase totals =	$1,104.53		$1,174.8163	$1,174.82	$1,174.85	$1,174.90