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	$159.85	11.600%	$178.3926	$178.39	$178.40	$178.40
Purchase #2	$116.92	7.620%	$125.8293	$125.83	$125.85	$125.80
Purchase #3	$39.74	6.368%	$42.2706	$42.27	$42.25	$42.30
Purchase #4	$193.83	4.667%	$202.876	$202.88	$202.90	$202.90
Purchase #5	$59.88	7.787%	$64.5429	$64.54	$64.55	$64.50
Purchase #6	$98.54	13.427%	$111.771	$111.77	$111.75	$111.80
Purchase #7	$145.50	3.233%	$150.204	$150.20	$150.20	$150.20
7 purchase totals =	$814.26		$875.8864	$875.88	$875.90	$875.90