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	$88.32	3.334%	$91.2646	$91.26	$91.25	$91.30
Purchase #2	$175.81	9.112%	$191.8298	$191.83	$191.85	$191.80
Purchase #3	$26.65	7.389%	$28.6192	$28.62	$28.60	$28.60
Purchase #4	$142.83	9.235%	$156.0204	$156.02	$156.00	$156.00
Purchase #5	$41.36	4.423%	$43.1894	$43.19	$43.20	$43.20
Purchase #6	$93.59	5.116%	$98.3781	$98.38	$98.40	$98.40
Purchase #7	$115.77	6.425%	$123.2082	$123.21	$123.20	$123.20
7 purchase totals =	$684.33		$732.5097	$732.51	$732.50	$732.50