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	$19.50	5.643%	$20.6004	$20.60	$20.60	$20.60
Purchase #2	$168.38	11.550%	$187.8279	$187.83	$187.85	$187.80
Purchase #3	$41.39	7.829%	$44.6304	$44.63	$44.65	$44.60
Purchase #4	$186.99	4.151%	$194.752	$194.75	$194.75	$194.80
Purchase #5	$224.90	5.654%	$237.6158	$237.62	$237.60	$237.60
Purchase #6	$54.91	8.481%	$59.5669	$59.57	$59.55	$59.60
Purchase #7	$127.40	11.112%	$141.5567	$141.56	$141.55	$141.60
7 purchase totals =	$823.47		$886.5501	$886.56	$886.55	$886.60