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	$88.28	10.245%	$97.3243	$97.32	$97.30	$97.30
Purchase #2	$228.72	11.499%	$255.0205	$255.02	$255.00	$255.00
Purchase #3	$54.55	5.107%	$57.3359	$57.34	$57.35	$57.30
Purchase #4	$54.56	10.721%	$60.4094	$60.41	$60.40	$60.40
Purchase #5	$245.52	11.792%	$274.4717	$274.47	$274.45	$274.50
Purchase #6	$111.76	3.327%	$115.4783	$115.48	$115.50	$115.50
Purchase #7	$200.61	10.160%	$220.992	$220.99	$221.00	$221.00
7 purchase totals =	$984.00		$1,081.0321	$1,081.03	$1,081.00	$1,081.00