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	$117.89	11.841%	$131.8494	$131.85	$131.85	$131.80
Purchase #2	$229.94	12.767%	$259.2964	$259.30	$259.30	$259.30
Purchase #3	$72.77	7.548%	$78.2627	$78.26	$78.25	$78.30
Purchase #4	$229.93	12.541%	$258.7655	$258.77	$258.75	$258.80
Purchase #5	$31.42	7.370%	$33.7357	$33.74	$33.75	$33.70
Purchase #6	$218.83	7.766%	$235.8243	$235.82	$235.80	$235.80
Purchase #7	$188.67	12.747%	$212.7198	$212.72	$212.70	$212.70
7 purchase totals =	$1,089.45		$1,210.4538	$1,210.46	$1,210.40	$1,210.40