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	$210.46	7.631%	$226.5202	$226.52	$226.50	$226.50
Purchase #2	$97.65	12.564%	$109.9187	$109.92	$109.90	$109.90
Purchase #3	$136.45	5.346%	$143.7446	$143.74	$143.75	$143.70
Purchase #4	$40.34	5.433%	$42.5317	$42.53	$42.55	$42.50
Purchase #5	$188.81	6.112%	$200.3501	$200.35	$200.35	$200.40
Purchase #6	$126.54	10.592%	$139.9431	$139.94	$139.95	$139.90
Purchase #7	$89.54	9.168%	$97.749	$97.75	$97.75	$97.70
7 purchase totals =	$889.79		$960.7574	$960.75	$960.75	$960.60