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	$169.76	4.288%	$177.0393	$177.04	$177.05	$177.00
Purchase #2	$127.69	11.592%	$142.4918	$142.49	$142.50	$142.50
Purchase #3	$52.78	13.515%	$59.9132	$59.91	$59.90	$59.90
Purchase #4	$36.94	3.727%	$38.3168	$38.32	$38.30	$38.30
Purchase #5	$243.47	10.688%	$269.4921	$269.49	$269.50	$269.50
Purchase #6	$207.43	12.397%	$233.1451	$233.15	$233.15	$233.10
Purchase #7	$243.90	8.457%	$264.5266	$264.53	$264.55	$264.50
7 purchase totals =	$1,081.97		$1,184.9249	$1,184.93	$1,184.95	$1,184.80