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	$69.98	5.475%	$73.8114	$73.81	$73.80	$73.80
Purchase #2	$168.30	9.663%	$184.5628	$184.56	$184.55	$184.60
Purchase #3	$47.70	6.299%	$50.7046	$50.70	$50.70	$50.70
Purchase #4	$196.53	10.104%	$216.3874	$216.39	$216.40	$216.40
Purchase #5	$179.38	3.577%	$185.7964	$185.80	$185.80	$185.80
Purchase #6	$185.41	11.578%	$206.8768	$206.88	$206.90	$206.90
Purchase #7	$87.87	3.455%	$90.9059	$90.91	$90.90	$90.90
7 purchase totals =	$935.17		$1,009.0453	$1,009.05	$1,009.05	$1,009.10