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	$123.32	3.192%	$127.2564	$127.26	$127.25	$127.30
Purchase #2	$43.40	6.139%	$46.0643	$46.06	$46.05	$46.10
Purchase #3	$45.33	13.228%	$51.3263	$51.33	$51.35	$51.30
Purchase #4	$76.27	11.481%	$85.0266	$85.03	$85.05	$85.00
Purchase #5	$181.86	13.151%	$205.7764	$205.78	$205.80	$205.80
Purchase #6	$245.84	3.414%	$254.233	$254.23	$254.25	$254.20
Purchase #7	$159.49	10.689%	$176.5379	$176.54	$176.55	$176.50
7 purchase totals =	$875.51		$946.2209	$946.23	$946.30	$946.20