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	$82.83	3.558%	$85.7771	$85.78	$85.80	$85.80
Purchase #2	$218.82	3.241%	$225.912	$225.91	$225.90	$225.90
Purchase #3	$182.89	8.456%	$198.3552	$198.36	$198.35	$198.40
Purchase #4	$139.33	6.707%	$148.6749	$148.67	$148.65	$148.70
Purchase #5	$110.98	5.764%	$117.3769	$117.38	$117.40	$117.40
Purchase #6	$179.56	13.364%	$203.5564	$203.56	$203.55	$203.60
Purchase #7	$226.89	12.672%	$255.6415	$255.64	$255.65	$255.60
7 purchase totals =	$1,141.30		$1,235.2940	$1,235.30	$1,235.30	$1,235.40