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	$198.52	7.571%	$213.5499	$213.55	$213.55	$213.50
Purchase #2	$128.63	7.103%	$137.7666	$137.77	$137.75	$137.80
Purchase #3	$146.77	10.595%	$162.3203	$162.32	$162.30	$162.30
Purchase #4	$181.92	3.849%	$188.9221	$188.92	$188.90	$188.90
Purchase #5	$66.96	6.621%	$71.3934	$71.39	$71.40	$71.40
Purchase #6	$71.53	5.276%	$75.3039	$75.30	$75.30	$75.30
Purchase #7	$109.56	12.655%	$123.4248	$123.42	$123.40	$123.40
7 purchase totals =	$903.89		$972.6810	$972.67	$972.60	$972.60