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	$172.40	7.309%	$185.0007	$185.00	$185.00	$185.00
Purchase #2	$166.56	13.381%	$188.8474	$188.85	$188.85	$188.80
Purchase #3	$109.47	5.124%	$115.0792	$115.08	$115.10	$115.10
Purchase #4	$119.74	11.683%	$133.7292	$133.73	$133.75	$133.70
Purchase #5	$94.69	5.533%	$99.9292	$99.93	$99.95	$99.90
Purchase #6	$188.40	5.382%	$198.5397	$198.54	$198.55	$198.50
Purchase #7	$196.27	12.794%	$221.3808	$221.38	$221.40	$221.40
7 purchase totals =	$1,047.53		$1,142.5062	$1,142.51	$1,142.60	$1,142.40