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	$203.61	12.690%	$229.4481	$229.45	$229.45	$229.40
Purchase #2	$61.36	6.259%	$65.2005	$65.20	$65.20	$65.20
Purchase #3	$10.34	10.343%	$11.4095	$11.41	$11.40	$11.40
Purchase #4	$80.26	3.797%	$83.3075	$83.31	$83.30	$83.30
Purchase #5	$95.60	6.855%	$102.1534	$102.15	$102.15	$102.20
Purchase #6	$204.39	11.236%	$227.3553	$227.36	$227.35	$227.40
Purchase #7	$248.77	4.402%	$259.7209	$259.72	$259.70	$259.70
7 purchase totals =	$904.33		$978.5952	$978.60	$978.55	$978.60