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	$14.34	4.311%	$14.9582	$14.96	$14.95	$15.00
Purchase #2	$95.57	7.847%	$103.0694	$103.07	$103.05	$103.10
Purchase #3	$24.47	13.773%	$27.8403	$27.84	$27.85	$27.80
Purchase #4	$185.55	13.741%	$211.0464	$211.05	$211.05	$211.00
Purchase #5	$103.30	13.700%	$117.4521	$117.45	$117.45	$117.50
Purchase #6	$159.71	4.150%	$166.338	$166.34	$166.35	$166.30
Purchase #7	$57.88	13.132%	$65.4808	$65.48	$65.50	$65.50
7 purchase totals =	$640.82		$706.1852	$706.19	$706.20	$706.20