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	$134.60	7.705%	$144.9709	$144.97	$144.95	$145.00
Purchase #2	$54.54	9.251%	$59.5855	$59.59	$59.60	$59.60
Purchase #3	$148.62	9.114%	$162.1652	$162.17	$162.15	$162.20
Purchase #4	$208.32	3.332%	$215.2612	$215.26	$215.25	$215.30
Purchase #5	$74.68	12.247%	$83.8261	$83.83	$83.85	$83.80
Purchase #6	$159.67	5.533%	$168.5045	$168.50	$168.50	$168.50
Purchase #7	$45.74	13.754%	$52.0311	$52.03	$52.05	$52.00
7 purchase totals =	$826.17		$886.3445	$886.35	$886.35	$886.40