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	$75.93	3.539%	$78.6172	$78.62	$78.60	$78.60
Purchase #2	$84.91	13.376%	$96.2676	$96.27	$96.25	$96.30
Purchase #3	$69.46	12.336%	$78.0286	$78.03	$78.05	$78.00
Purchase #4	$222.64	12.573%	$250.6325	$250.63	$250.65	$250.60
Purchase #5	$118.99	10.873%	$131.9278	$131.93	$131.95	$131.90
Purchase #6	$103.62	6.119%	$109.9605	$109.96	$109.95	$110.00
Purchase #7	$186.86	6.686%	$199.3535	$199.35	$199.35	$199.40
7 purchase totals =	$862.41		$944.7877	$944.79	$944.80	$944.80