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	$241.79	7.488%	$259.8952	$259.90	$259.90	$259.90
Purchase #2	$201.74	8.559%	$219.0069	$219.01	$219.00	$219.00
Purchase #3	$70.36	11.479%	$78.4366	$78.44	$78.45	$78.40
Purchase #4	$207.46	4.309%	$216.3995	$216.40	$216.40	$216.40
Purchase #5	$137.63	7.285%	$147.6563	$147.66	$147.65	$147.70
Purchase #6	$66.41	9.510%	$72.7256	$72.73	$72.75	$72.70
Purchase #7	$161.63	4.412%	$168.7611	$168.76	$168.75	$168.80
7 purchase totals =	$1,087.02		$1,162.8812	$1,162.90	$1,162.90	$1,162.90