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	$41.56	12.593%	$46.7937	$46.79	$46.80	$46.80
Purchase #2	$79.76	7.238%	$85.533	$85.53	$85.55	$85.50
Purchase #3	$179.43	9.563%	$196.5889	$196.59	$196.60	$196.60
Purchase #4	$156.53	6.562%	$166.8015	$166.80	$166.80	$166.80
Purchase #5	$98.45	5.606%	$103.9691	$103.97	$103.95	$104.00
Purchase #6	$100.54	13.692%	$114.3059	$114.31	$114.30	$114.30
Purchase #7	$108.52	5.439%	$114.4224	$114.42	$114.40	$114.40
7 purchase totals =	$764.79		$828.4145	$828.41	$828.40	$828.40