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	$178.98	3.189%	$184.6877	$184.69	$184.70	$184.70
Purchase #2	$80.66	11.212%	$89.7036	$89.70	$89.70	$89.70
Purchase #3	$12.32	5.387%	$12.9837	$12.98	$13.00	$13.00
Purchase #4	$84.65	13.489%	$96.0684	$96.07	$96.05	$96.10
Purchase #5	$178.49	3.607%	$184.9281	$184.93	$184.95	$184.90
Purchase #6	$88.32	3.382%	$91.307	$91.31	$91.30	$91.30
Purchase #7	$43.48	3.799%	$45.1318	$45.13	$45.15	$45.10
7 purchase totals =	$666.90		$704.8103	$704.81	$704.85	$704.80