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	$52.73	11.557%	$58.824	$58.82	$58.80	$58.80
Purchase #2	$93.86	5.633%	$99.1471	$99.15	$99.15	$99.10
Purchase #3	$215.82	11.791%	$241.2673	$241.27	$241.25	$241.30
Purchase #4	$164.55	3.822%	$170.8391	$170.84	$170.85	$170.80
Purchase #5	$35.57	3.505%	$36.8167	$36.82	$36.80	$36.80
Purchase #6	$144.35	7.804%	$155.6151	$155.62	$155.60	$155.60
Purchase #7	$231.94	11.475%	$258.5551	$258.56	$258.55	$258.60
7 purchase totals =	$938.82		$1,021.0644	$1,021.08	$1,021.00	$1,021.00