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	$193.91	7.406%	$208.271	$208.27	$208.25	$208.30
Purchase #2	$101.91	6.216%	$108.2447	$108.24	$108.25	$108.20
Purchase #3	$73.62	10.425%	$81.2949	$81.29	$81.30	$81.30
Purchase #4	$138.88	5.378%	$146.349	$146.35	$146.35	$146.30
Purchase #5	$184.32	6.718%	$196.7026	$196.70	$196.70	$196.70
Purchase #6	$89.33	3.401%	$92.3681	$92.37	$92.35	$92.40
Purchase #7	$80.52	12.433%	$90.5311	$90.53	$90.55	$90.50
7 purchase totals =	$862.49		$923.7614	$923.75	$923.75	$923.70