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	$37.32	10.505%	$41.2405	$41.24	$41.25	$41.20
Purchase #2	$184.59	11.627%	$206.0523	$206.05	$206.05	$206.10
Purchase #3	$239.82	13.368%	$271.8791	$271.88	$271.90	$271.90
Purchase #4	$186.48	5.396%	$196.5425	$196.54	$196.55	$196.50
Purchase #5	$60.43	12.412%	$67.9306	$67.93	$67.95	$67.90
Purchase #6	$188.49	5.282%	$198.446	$198.45	$198.45	$198.40
Purchase #7	$121.53	13.209%	$137.5829	$137.58	$137.60	$137.60
7 purchase totals =	$1,018.66		$1,119.6739	$1,119.67	$1,119.75	$1,119.60