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	$203.85	6.311%	$216.715	$216.72	$216.70	$216.70
Purchase #2	$63.82	13.602%	$72.5008	$72.50	$72.50	$72.50
Purchase #3	$73.65	5.219%	$77.4938	$77.49	$77.50	$77.50
Purchase #4	$209.96	13.123%	$237.5131	$237.51	$237.50	$237.50
Purchase #5	$228.57	6.527%	$243.4888	$243.49	$243.50	$243.50
Purchase #6	$26.85	3.602%	$27.8171	$27.82	$27.80	$27.80
Purchase #7	$50.41	5.231%	$53.0469	$53.05	$53.05	$53.00
7 purchase totals =	$857.11		$928.5755	$928.58	$928.55	$928.50