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	$174.35	5.855%	$184.5582	$184.56	$184.55	$184.60
Purchase #2	$138.38	12.865%	$156.1826	$156.18	$156.20	$156.20
Purchase #3	$200.60	10.231%	$221.1234	$221.12	$221.10	$221.10
Purchase #4	$14.40	10.320%	$15.8861	$15.89	$15.90	$15.90
Purchase #5	$110.79	3.321%	$114.4693	$114.47	$114.45	$114.50
Purchase #6	$180.30	13.814%	$205.2066	$205.21	$205.20	$205.20
Purchase #7	$145.73	4.222%	$151.8827	$151.88	$151.90	$151.90
7 purchase totals =	$964.55		$1,049.3089	$1,049.31	$1,049.30	$1,049.40