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	$162.45	5.602%	$171.5504	$171.55	$171.55	$171.60
Purchase #2	$5.95	3.565%	$6.1621	$6.16	$6.15	$6.20
Purchase #3	$99.71	13.748%	$113.4181	$113.42	$113.40	$113.40
Purchase #4	$164.97	12.649%	$185.8371	$185.84	$185.85	$185.80
Purchase #5	$25.78	5.215%	$27.1244	$27.12	$27.10	$27.10
Purchase #6	$246.81	13.555%	$280.2651	$280.27	$280.25	$280.30
Purchase #7	$54.65	8.717%	$59.4138	$59.41	$59.40	$59.40
7 purchase totals =	$760.32		$843.7710	$843.77	$843.70	$843.80