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	$100.86	5.854%	$106.7643	$106.76	$106.75	$106.80
Purchase #2	$71.82	9.636%	$78.7406	$78.74	$78.75	$78.70
Purchase #3	$29.37	8.286%	$31.8036	$31.80	$31.80	$31.80
Purchase #4	$72.39	12.652%	$81.5488	$81.55	$81.55	$81.50
Purchase #5	$107.43	11.305%	$119.575	$119.58	$119.60	$119.60
Purchase #6	$212.77	5.115%	$223.6532	$223.65	$223.65	$223.70
Purchase #7	$97.54	12.501%	$109.7335	$109.73	$109.75	$109.70
7 purchase totals =	$692.18		$751.8190	$751.81	$751.85	$751.80