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	$222.91	12.659%	$251.1282	$251.13	$251.15	$251.10
Purchase #2	$81.52	9.250%	$89.0606	$89.06	$89.05	$89.10
Purchase #3	$57.88	3.584%	$59.9544	$59.95	$59.95	$60.00
Purchase #4	$118.86	10.445%	$131.2749	$131.27	$131.25	$131.30
Purchase #5	$44.92	6.447%	$47.816	$47.82	$47.80	$47.80
Purchase #6	$58.29	9.831%	$64.0205	$64.02	$64.00	$64.00
Purchase #7	$83.42	12.732%	$94.041	$94.04	$94.05	$94.00
7 purchase totals =	$667.80		$737.2956	$737.29	$737.25	$737.30