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	$89.87	6.329%	$95.5579	$95.56	$95.55	$95.60
Purchase #2	$75.77	5.588%	$80.004	$80.00	$80.00	$80.00
Purchase #3	$97.91	9.664%	$107.372	$107.37	$107.35	$107.40
Purchase #4	$238.81	11.603%	$266.5191	$266.52	$266.50	$266.50
Purchase #5	$41.36	7.308%	$44.3826	$44.38	$44.40	$44.40
Purchase #6	$235.77	8.809%	$256.539	$256.54	$256.55	$256.50
Purchase #7	$152.79	10.356%	$168.6129	$168.61	$168.60	$168.60
7 purchase totals =	$932.28		$1,018.9875	$1,018.98	$1,018.95	$1,019.00