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	$82.76	4.465%	$86.4552	$86.46	$86.45	$86.50
Purchase #2	$202.70	9.860%	$222.6862	$222.69	$222.70	$222.70
Purchase #3	$166.61	13.645%	$189.3439	$189.34	$189.35	$189.30
Purchase #4	$188.84	12.651%	$212.7301	$212.73	$212.75	$212.70
Purchase #5	$157.66	8.696%	$171.3701	$171.37	$171.35	$171.40
Purchase #6	$20.39	8.331%	$22.0887	$22.09	$22.10	$22.10
Purchase #7	$89.60	10.410%	$98.9274	$98.93	$98.95	$98.90
7 purchase totals =	$908.56		$1,003.6016	$1,003.61	$1,003.65	$1,003.60