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	$179.52	3.583%	$185.9522	$185.95	$185.95	$186.00
Purchase #2	$72.67	13.345%	$82.3678	$82.37	$82.35	$82.40
Purchase #3	$159.37	3.449%	$164.8667	$164.87	$164.85	$164.90
Purchase #4	$225.66	11.606%	$251.8501	$251.85	$251.85	$251.90
Purchase #5	$217.66	11.379%	$242.4275	$242.43	$242.45	$242.40
Purchase #6	$236.77	11.443%	$263.8636	$263.86	$263.85	$263.90
Purchase #7	$161.75	3.316%	$167.1136	$167.11	$167.10	$167.10
7 purchase totals =	$1,253.40		$1,358.4415	$1,358.44	$1,358.40	$1,358.60