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	$72.28	8.113%	$78.1441	$78.14	$78.15	$78.10
Purchase #2	$178.93	3.576%	$185.3285	$185.33	$185.35	$185.30
Purchase #3	$51.82	5.300%	$54.5665	$54.57	$54.55	$54.60
Purchase #4	$62.45	10.616%	$69.0797	$69.08	$69.10	$69.10
Purchase #5	$105.86	10.658%	$117.1426	$117.14	$117.15	$117.10
Purchase #6	$55.41	6.214%	$58.8532	$58.85	$58.85	$58.90
Purchase #7	$116.90	10.357%	$129.0073	$129.01	$129.00	$129.00
7 purchase totals =	$643.65		$692.1219	$692.12	$692.15	$692.10