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	$32.79	13.815%	$37.3199	$37.32	$37.30	$37.30
Purchase #2	$230.88	3.555%	$239.0878	$239.09	$239.10	$239.10
Purchase #3	$147.45	7.315%	$158.236	$158.24	$158.25	$158.20
Purchase #4	$178.89	11.139%	$198.8166	$198.82	$198.80	$198.80
Purchase #5	$149.82	4.642%	$156.7746	$156.77	$156.75	$156.80
Purchase #6	$110.53	10.812%	$122.4805	$122.48	$122.50	$122.50
Purchase #7	$174.28	6.455%	$185.5298	$185.53	$185.55	$185.50
7 purchase totals =	$1,024.64		$1,098.2452	$1,098.25	$1,098.25	$1,098.20