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	$247.96	4.499%	$259.1157	$259.12	$259.10	$259.10
Purchase #2	$82.73	4.589%	$86.5265	$86.53	$86.55	$86.50
Purchase #3	$196.30	6.741%	$209.5326	$209.53	$209.55	$209.50
Purchase #4	$49.46	11.811%	$55.3017	$55.30	$55.30	$55.30
Purchase #5	$167.90	11.179%	$186.6695	$186.67	$186.65	$186.70
Purchase #6	$144.82	13.677%	$164.627	$164.63	$164.65	$164.60
Purchase #7	$206.74	4.371%	$215.7766	$215.78	$215.80	$215.80
7 purchase totals =	$1,095.91		$1,177.5496	$1,177.56	$1,177.60	$1,177.50