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	$178.95	9.848%	$196.573	$196.57	$196.55	$196.60
Purchase #2	$233.46	12.556%	$262.7732	$262.77	$262.75	$262.80
Purchase #3	$81.97	5.274%	$86.2931	$86.29	$86.30	$86.30
Purchase #4	$167.98	12.458%	$188.9069	$188.91	$188.90	$188.90
Purchase #5	$128.31	4.226%	$133.7324	$133.73	$133.75	$133.70
Purchase #6	$179.60	13.596%	$204.0184	$204.02	$204.00	$204.00
Purchase #7	$54.61	8.862%	$59.4495	$59.45	$59.45	$59.40
7 purchase totals =	$1,024.88		$1,131.7465	$1,131.74	$1,131.70	$1,131.70