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	$171.75	3.801%	$178.2782	$178.28	$178.30	$178.30
Purchase #2	$213.97	4.659%	$223.9389	$223.94	$223.95	$223.90
Purchase #3	$64.30	3.831%	$66.7633	$66.76	$66.75	$66.80
Purchase #4	$138.61	12.466%	$155.8891	$155.89	$155.90	$155.90
Purchase #5	$234.79	5.864%	$248.5581	$248.56	$248.55	$248.60
Purchase #6	$116.41	9.406%	$127.3595	$127.36	$127.35	$127.40
Purchase #7	$76.88	7.760%	$82.8459	$82.85	$82.85	$82.80
7 purchase totals =	$1,016.71		$1,083.6330	$1,083.64	$1,083.65	$1,083.70