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	$67.98	7.835%	$73.3062	$73.31	$73.30	$73.30
Purchase #2	$67.82	7.280%	$72.7573	$72.76	$72.75	$72.80
Purchase #3	$234.68	5.792%	$248.2727	$248.27	$248.25	$248.30
Purchase #4	$177.69	3.772%	$184.3925	$184.39	$184.40	$184.40
Purchase #5	$55.31	12.830%	$62.4063	$62.41	$62.40	$62.40
Purchase #6	$246.55	6.599%	$262.8198	$262.82	$262.80	$262.80
Purchase #7	$134.85	13.270%	$152.7446	$152.74	$152.75	$152.70
7 purchase totals =	$984.88		$1,056.6994	$1,056.70	$1,056.65	$1,056.70