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	$186.61	4.105%	$194.2703	$194.27	$194.25	$194.30
Purchase #2	$45.26	3.630%	$46.9029	$46.90	$46.90	$46.90
Purchase #3	$168.87	10.547%	$186.6807	$186.68	$186.70	$186.70
Purchase #4	$203.56	7.873%	$219.5863	$219.59	$219.60	$219.60
Purchase #5	$234.59	11.623%	$261.8564	$261.86	$261.85	$261.90
Purchase #6	$57.66	6.861%	$61.6161	$61.62	$61.60	$61.60
Purchase #7	$188.78	13.455%	$214.1803	$214.18	$214.20	$214.20
7 purchase totals =	$1,085.33		$1,185.0930	$1,185.10	$1,185.10	$1,185.20