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	$132.94	11.436%	$148.143	$148.14	$148.15	$148.10
Purchase #2	$209.85	3.697%	$217.6082	$217.61	$217.60	$217.60
Purchase #3	$168.27	10.331%	$185.654	$185.65	$185.65	$185.70
Purchase #4	$44.72	3.790%	$46.4149	$46.41	$46.40	$46.40
Purchase #5	$73.30	9.254%	$80.0832	$80.08	$80.10	$80.10
Purchase #6	$212.34	4.328%	$221.5301	$221.53	$221.55	$221.50
Purchase #7	$153.35	13.831%	$174.5598	$174.56	$174.55	$174.60
7 purchase totals =	$994.77		$1,073.9932	$1,073.98	$1,074.00	$1,074.00