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	$150.99	11.782%	$168.7796	$168.78	$168.80	$168.80
Purchase #2	$114.76	9.472%	$125.6301	$125.63	$125.65	$125.60
Purchase #3	$114.41	12.656%	$128.8897	$128.89	$128.90	$128.90
Purchase #4	$221.65	10.510%	$244.9454	$244.95	$244.95	$244.90
Purchase #5	$160.97	4.121%	$167.6036	$167.60	$167.60	$167.60
Purchase #6	$240.64	5.198%	$253.1485	$253.15	$253.15	$253.10
Purchase #7	$41.43	9.869%	$45.5187	$45.52	$45.50	$45.50
7 purchase totals =	$1,044.85		$1,134.5156	$1,134.52	$1,134.55	$1,134.40