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	$37.29	3.328%	$38.531	$38.53	$38.55	$38.50
Purchase #2	$196.96	4.399%	$205.6243	$205.62	$205.60	$205.60
Purchase #3	$6.68	11.158%	$7.4254	$7.43	$7.45	$7.40
Purchase #4	$210.60	13.426%	$238.8752	$238.88	$238.90	$238.90
Purchase #5	$77.25	11.699%	$86.2875	$86.29	$86.30	$86.30
Purchase #6	$84.57	7.543%	$90.9491	$90.95	$90.95	$90.90
Purchase #7	$229.66	7.869%	$247.7319	$247.73	$247.75	$247.70
7 purchase totals =	$843.01		$915.4244	$915.43	$915.50	$915.30