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	$141.42	4.312%	$147.518	$147.52	$147.50	$147.50
Purchase #2	$41.75	4.615%	$43.6768	$43.68	$43.70	$43.70
Purchase #3	$29.76	13.751%	$33.8523	$33.85	$33.85	$33.90
Purchase #4	$109.63	12.799%	$123.6615	$123.66	$123.65	$123.70
Purchase #5	$90.34	9.116%	$98.5754	$98.58	$98.60	$98.60
Purchase #6	$93.78	6.341%	$99.7266	$99.73	$99.75	$99.70
Purchase #7	$30.71	3.149%	$31.6771	$31.68	$31.70	$31.70
7 purchase totals =	$537.39		$578.6877	$578.70	$578.75	$578.80