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	$102.64	8.699%	$111.5687	$111.57	$111.55	$111.60
Purchase #2	$28.25	3.674%	$29.2879	$29.29	$29.30	$29.30
Purchase #3	$185.66	13.156%	$210.0854	$210.09	$210.10	$210.10
Purchase #4	$179.62	11.119%	$199.5919	$199.59	$199.60	$199.60
Purchase #5	$246.28	5.215%	$259.1235	$259.12	$259.10	$259.10
Purchase #6	$103.25	7.778%	$111.2808	$111.28	$111.30	$111.30
Purchase #7	$213.36	7.444%	$229.2425	$229.24	$229.25	$229.20
7 purchase totals =	$1,059.06		$1,150.1807	$1,150.18	$1,150.20	$1,150.20