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	$241.38	7.186%	$258.7256	$258.73	$258.75	$258.70
Purchase #2	$13.87	7.464%	$14.9053	$14.91	$14.90	$14.90
Purchase #3	$87.71	13.539%	$99.5851	$99.59	$99.60	$99.60
Purchase #4	$32.41	4.608%	$33.9035	$33.90	$33.90	$33.90
Purchase #5	$205.55	11.683%	$229.5644	$229.56	$229.55	$229.60
Purchase #6	$102.73	7.200%	$110.1266	$110.13	$110.15	$110.10
Purchase #7	$36.86	7.534%	$39.637	$39.64	$39.65	$39.60
7 purchase totals =	$720.51		$786.4475	$786.46	$786.50	$786.40