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	$54.45	8.372%	$59.0086	$59.01	$59.00	$59.00
Purchase #2	$250.86	11.674%	$280.1454	$280.15	$280.15	$280.10
Purchase #3	$243.55	9.754%	$267.3059	$267.31	$267.30	$267.30
Purchase #4	$194.93	5.454%	$205.5615	$205.56	$205.55	$205.60
Purchase #5	$108.76	4.282%	$113.4171	$113.42	$113.40	$113.40
Purchase #6	$39.83	10.605%	$44.054	$44.05	$44.05	$44.10
Purchase #7	$231.58	4.689%	$242.4388	$242.44	$242.45	$242.40
7 purchase totals =	$1,123.96		$1,211.9313	$1,211.94	$1,211.90	$1,211.90