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	$59.42	9.166%	$64.8664	$64.87	$64.85	$64.90
Purchase #2	$171.59	5.611%	$181.2179	$181.22	$181.20	$181.20
Purchase #3	$188.83	13.502%	$214.3258	$214.33	$214.35	$214.30
Purchase #4	$197.71	13.204%	$223.8156	$223.82	$223.80	$223.80
Purchase #5	$159.68	5.821%	$168.975	$168.98	$169.00	$169.00
Purchase #6	$59.75	3.868%	$62.0611	$62.06	$62.05	$62.10
Purchase #7	$188.33	10.546%	$208.1913	$208.19	$208.20	$208.20
7 purchase totals =	$1,025.31		$1,123.4531	$1,123.47	$1,123.45	$1,123.50