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	$60.75	6.722%	$64.8336	$64.83	$64.85	$64.80
Purchase #2	$138.84	6.864%	$148.37	$148.37	$148.35	$148.40
Purchase #3	$178.45	9.425%	$195.2689	$195.27	$195.25	$195.30
Purchase #4	$78.88	13.603%	$89.61	$89.61	$89.60	$89.60
Purchase #5	$93.74	7.489%	$100.7602	$100.76	$100.75	$100.80
Purchase #6	$73.46	10.749%	$81.3562	$81.36	$81.35	$81.40
Purchase #7	$196.40	6.129%	$208.4374	$208.44	$208.45	$208.40
7 purchase totals =	$820.52		$888.6363	$888.64	$888.60	$888.70