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	$50.47	5.465%	$53.2282	$53.23	$53.25	$53.20
Purchase #2	$147.99	7.780%	$159.5036	$159.50	$159.50	$159.50
Purchase #3	$101.57	3.343%	$104.9655	$104.97	$104.95	$105.00
Purchase #4	$53.70	6.390%	$57.1314	$57.13	$57.15	$57.10
Purchase #5	$21.89	10.457%	$24.179	$24.18	$24.20	$24.20
Purchase #6	$121.76	13.334%	$137.9955	$138.00	$138.00	$138.00
Purchase #7	$86.34	3.190%	$89.0942	$89.09	$89.10	$89.10
7 purchase totals =	$583.72		$626.0974	$626.10	$626.15	$626.10