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	$113.90	11.759%	$127.2935	$127.29	$127.30	$127.30
Purchase #2	$114.65	8.532%	$124.4319	$124.43	$124.45	$124.40
Purchase #3	$131.90	9.409%	$144.3105	$144.31	$144.30	$144.30
Purchase #4	$77.71	11.410%	$86.5767	$86.58	$86.60	$86.60
Purchase #5	$73.82	7.730%	$79.5263	$79.53	$79.55	$79.50
Purchase #6	$236.92	13.344%	$268.5346	$268.53	$268.55	$268.50
Purchase #7	$178.60	4.548%	$186.7227	$186.72	$186.70	$186.70
7 purchase totals =	$927.50		$1,017.3962	$1,017.39	$1,017.45	$1,017.30