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	$61.53	6.104%	$65.2858	$65.29	$65.30	$65.30
Purchase #2	$106.46	7.732%	$114.6915	$114.69	$114.70	$114.70
Purchase #3	$35.68	4.465%	$37.2731	$37.27	$37.25	$37.30
Purchase #4	$188.59	5.304%	$198.5928	$198.59	$198.60	$198.60
Purchase #5	$228.96	3.474%	$236.9141	$236.91	$236.90	$236.90
Purchase #6	$31.98	4.503%	$33.4201	$33.42	$33.40	$33.40
Purchase #7	$185.96	4.738%	$194.7708	$194.77	$194.75	$194.80
7 purchase totals =	$839.16		$880.9482	$880.94	$880.90	$881.00