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	$115.62	6.156%	$122.7376	$122.74	$122.75	$122.70
Purchase #2	$173.82	9.173%	$189.7645	$189.76	$189.75	$189.80
Purchase #3	$85.89	5.526%	$90.6363	$90.64	$90.65	$90.60
Purchase #4	$232.98	13.670%	$264.8284	$264.83	$264.85	$264.80
Purchase #5	$182.94	3.180%	$188.7575	$188.76	$188.75	$188.80
Purchase #6	$233.29	7.423%	$250.6071	$250.61	$250.60	$250.60
Purchase #7	$94.51	9.663%	$103.6425	$103.64	$103.65	$103.60
7 purchase totals =	$1,119.05		$1,210.9739	$1,210.98	$1,211.00	$1,210.90