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	$222.71	13.807%	$253.4596	$253.46	$253.45	$253.50
Purchase #2	$151.59	3.180%	$156.4106	$156.41	$156.40	$156.40
Purchase #3	$11.87	11.625%	$13.2499	$13.25	$13.25	$13.20
Purchase #4	$176.25	7.168%	$188.8836	$188.88	$188.90	$188.90
Purchase #5	$194.87	4.313%	$203.2747	$203.27	$203.25	$203.30
Purchase #6	$220.25	3.599%	$228.1768	$228.18	$228.20	$228.20
Purchase #7	$29.88	6.703%	$31.8829	$31.88	$31.90	$31.90
7 purchase totals =	$1,007.42		$1,075.3381	$1,075.33	$1,075.35	$1,075.40