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	$200.32	11.529%	$223.4149	$223.41	$223.40	$223.40
Purchase #2	$231.54	7.295%	$248.4308	$248.43	$248.45	$248.40
Purchase #3	$139.32	5.234%	$146.612	$146.61	$146.60	$146.60
Purchase #4	$171.81	3.827%	$178.3852	$178.39	$178.40	$178.40
Purchase #5	$248.84	5.814%	$263.3076	$263.31	$263.30	$263.30
Purchase #6	$131.99	3.399%	$136.4763	$136.48	$136.50	$136.50
Purchase #7	$245.40	10.640%	$271.5106	$271.51	$271.50	$271.50
7 purchase totals =	$1,369.22		$1,468.1374	$1,468.14	$1,468.15	$1,468.10