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	$104.71	4.689%	$109.6199	$109.62	$109.60	$109.60
Purchase #2	$26.65	3.860%	$27.6787	$27.68	$27.70	$27.70
Purchase #3	$194.67	10.603%	$215.3109	$215.31	$215.30	$215.30
Purchase #4	$230.39	13.577%	$261.6701	$261.67	$261.65	$261.70
Purchase #5	$205.78	8.682%	$223.6458	$223.65	$223.65	$223.60
Purchase #6	$97.61	8.456%	$105.8639	$105.86	$105.85	$105.90
Purchase #7	$171.89	7.272%	$184.3898	$184.39	$184.40	$184.40
7 purchase totals =	$1,031.70		$1,128.1791	$1,128.18	$1,128.15	$1,128.20