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	$33.63	12.597%	$37.8664	$37.87	$37.85	$37.90
Purchase #2	$219.93	4.253%	$229.2836	$229.28	$229.30	$229.30
Purchase #3	$201.77	7.818%	$217.5444	$217.54	$217.55	$217.50
Purchase #4	$16.54	13.874%	$18.8348	$18.83	$18.85	$18.80
Purchase #5	$157.89	6.665%	$168.4134	$168.41	$168.40	$168.40
Purchase #6	$234.87	4.436%	$245.2888	$245.29	$245.30	$245.30
Purchase #7	$82.82	13.576%	$94.0636	$94.06	$94.05	$94.10
7 purchase totals =	$947.45		$1,011.2950	$1,011.28	$1,011.30	$1,011.30