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	$130.62	10.559%	$144.4122	$144.41	$144.40	$144.40
Purchase #2	$248.28	7.769%	$267.5689	$267.57	$267.55	$267.60
Purchase #3	$121.71	8.333%	$131.8521	$131.85	$131.85	$131.90
Purchase #4	$161.31	6.331%	$171.5225	$171.52	$171.50	$171.50
Purchase #5	$159.80	5.371%	$168.3829	$168.38	$168.40	$168.40
Purchase #6	$135.75	11.451%	$151.2947	$151.29	$151.30	$151.30
Purchase #7	$107.37	8.337%	$116.3214	$116.32	$116.30	$116.30
7 purchase totals =	$1,064.84		$1,151.3547	$1,151.34	$1,151.30	$1,151.40