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	$234.34	11.649%	$261.6383	$261.64	$261.65	$261.60
Purchase #2	$158.40	9.563%	$173.5478	$173.55	$173.55	$173.50
Purchase #3	$53.71	6.454%	$57.1764	$57.18	$57.20	$57.20
Purchase #4	$131.48	9.752%	$144.3019	$144.30	$144.30	$144.30
Purchase #5	$7.81	12.787%	$8.8087	$8.81	$8.80	$8.80
Purchase #6	$113.71	12.429%	$127.843	$127.84	$127.85	$127.80
Purchase #7	$242.25	12.488%	$272.5022	$272.50	$272.50	$272.50
7 purchase totals =	$941.70		$1,045.8183	$1,045.82	$1,045.85	$1,045.70