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	$178.38	10.251%	$196.6657	$196.67	$196.65	$196.70
Purchase #2	$177.45	11.374%	$197.6332	$197.63	$197.65	$197.60
Purchase #3	$74.45	10.354%	$82.1586	$82.16	$82.15	$82.20
Purchase #4	$175.77	12.866%	$198.3846	$198.38	$198.40	$198.40
Purchase #5	$39.64	6.600%	$42.2562	$42.26	$42.25	$42.30
Purchase #6	$135.98	9.109%	$148.3664	$148.37	$148.35	$148.40
Purchase #7	$118.76	8.197%	$128.4948	$128.49	$128.50	$128.50
7 purchase totals =	$900.43		$993.9595	$993.96	$993.95	$994.10