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	$81.51	4.173%	$84.9114	$84.91	$84.90	$84.90
Purchase #2	$97.93	8.107%	$105.8692	$105.87	$105.85	$105.90
Purchase #3	$150.77	11.773%	$168.5202	$168.52	$168.50	$168.50
Purchase #4	$138.94	9.499%	$152.1379	$152.14	$152.15	$152.10
Purchase #5	$210.44	8.466%	$228.2559	$228.26	$228.25	$228.30
Purchase #6	$200.59	8.849%	$218.3402	$218.34	$218.35	$218.30
Purchase #7	$52.64	8.471%	$57.0991	$57.10	$57.10	$57.10
7 purchase totals =	$932.82		$1,015.1339	$1,015.14	$1,015.10	$1,015.10