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	$62.38	6.191%	$66.2419	$66.24	$66.25	$66.20
Purchase #2	$228.93	8.573%	$248.5562	$248.56	$248.55	$248.60
Purchase #3	$236.77	3.414%	$244.8533	$244.85	$244.85	$244.90
Purchase #4	$139.62	9.481%	$152.8574	$152.86	$152.85	$152.90
Purchase #5	$171.76	4.461%	$179.4222	$179.42	$179.40	$179.40
Purchase #6	$39.87	13.579%	$45.2839	$45.28	$45.30	$45.30
Purchase #7	$168.97	3.383%	$174.6863	$174.69	$174.70	$174.70
7 purchase totals =	$1,048.30		$1,111.9012	$1,111.90	$1,111.90	$1,112.00