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	$127.84	3.624%	$132.4729	$132.47	$132.45	$132.50
Purchase #2	$237.60	7.450%	$255.3012	$255.30	$255.30	$255.30
Purchase #3	$170.53	7.255%	$182.902	$182.90	$182.90	$182.90
Purchase #4	$245.89	9.773%	$269.9208	$269.92	$269.90	$269.90
Purchase #5	$125.82	10.317%	$138.8008	$138.80	$138.80	$138.80
Purchase #6	$160.82	8.443%	$174.398	$174.40	$174.40	$174.40
Purchase #7	$78.81	11.300%	$87.7155	$87.72	$87.70	$87.70
7 purchase totals =	$1,147.31		$1,241.5112	$1,241.51	$1,241.45	$1,241.50