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	$47.37	6.511%	$50.4543	$50.45	$50.45	$50.50
Purchase #2	$198.37	12.139%	$222.4501	$222.45	$222.45	$222.50
Purchase #3	$29.95	11.363%	$33.3532	$33.35	$33.35	$33.40
Purchase #4	$95.63	4.303%	$99.745	$99.75	$99.75	$99.70
Purchase #5	$249.65	6.443%	$265.7349	$265.73	$265.75	$265.70
Purchase #6	$201.49	6.169%	$213.9199	$213.92	$213.90	$213.90
Purchase #7	$133.51	7.792%	$143.9131	$143.91	$143.90	$143.90
7 purchase totals =	$955.97		$1,029.5705	$1,029.56	$1,029.55	$1,029.60