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	$100.44	5.393%	$105.8567	$105.86	$105.85	$105.90
Purchase #2	$187.85	9.638%	$205.955	$205.96	$205.95	$206.00
Purchase #3	$39.25	7.822%	$42.3201	$42.32	$42.30	$42.30
Purchase #4	$183.79	10.868%	$203.7643	$203.76	$203.75	$203.80
Purchase #5	$89.56	12.727%	$100.9583	$100.96	$100.95	$101.00
Purchase #6	$56.61	8.397%	$61.3635	$61.36	$61.35	$61.40
Purchase #7	$239.55	4.431%	$250.1645	$250.16	$250.15	$250.20
7 purchase totals =	$897.05		$970.3824	$970.38	$970.30	$970.60