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	$48.50	10.401%	$53.5445	$53.54	$53.55	$53.50
Purchase #2	$173.95	13.168%	$196.8557	$196.86	$196.85	$196.90
Purchase #3	$116.38	8.154%	$125.8696	$125.87	$125.85	$125.90
Purchase #4	$76.67	10.251%	$84.5294	$84.53	$84.55	$84.50
Purchase #5	$245.27	4.267%	$255.7357	$255.74	$255.75	$255.70
Purchase #6	$120.44	7.604%	$129.5983	$129.60	$129.60	$129.60
Purchase #7	$51.61	3.140%	$53.2306	$53.23	$53.25	$53.20
7 purchase totals =	$832.82		$899.3638	$899.37	$899.40	$899.30