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	$63.78	13.364%	$72.3036	$72.30	$72.30	$72.30
Purchase #2	$198.67	10.127%	$218.7893	$218.79	$218.80	$218.80
Purchase #3	$65.99	8.581%	$71.6526	$71.65	$71.65	$71.70
Purchase #4	$80.78	13.427%	$91.6263	$91.63	$91.65	$91.60
Purchase #5	$235.98	12.624%	$265.7701	$265.77	$265.75	$265.80
Purchase #6	$233.61	9.302%	$255.3404	$255.34	$255.35	$255.30
Purchase #7	$119.62	13.372%	$135.6156	$135.62	$135.60	$135.60
7 purchase totals =	$998.43		$1,111.0979	$1,111.10	$1,111.10	$1,111.10