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	$109.28	3.765%	$113.3944	$113.39	$113.40	$113.40
Purchase #2	$93.83	13.233%	$106.2465	$106.25	$106.25	$106.20
Purchase #3	$37.93	13.830%	$43.1757	$43.18	$43.20	$43.20
Purchase #4	$96.56	6.807%	$103.1328	$103.13	$103.15	$103.10
Purchase #5	$60.41	12.379%	$67.8882	$67.89	$67.90	$67.90
Purchase #6	$170.26	7.137%	$182.4115	$182.41	$182.40	$182.40
Purchase #7	$158.78	9.275%	$173.5068	$173.51	$173.50	$173.50
7 purchase totals =	$727.05		$789.7559	$789.76	$789.80	$789.70