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	$127.56	5.636%	$134.7493	$134.75	$134.75	$134.70
Purchase #2	$174.43	13.838%	$198.5676	$198.57	$198.55	$198.60
Purchase #3	$165.69	11.521%	$184.7791	$184.78	$184.80	$184.80
Purchase #4	$72.95	7.613%	$78.5037	$78.50	$78.50	$78.50
Purchase #5	$156.76	7.584%	$168.6487	$168.65	$168.65	$168.60
Purchase #6	$182.91	12.681%	$206.1048	$206.10	$206.10	$206.10
Purchase #7	$164.47	9.626%	$180.3019	$180.30	$180.30	$180.30
7 purchase totals =	$1,044.77		$1,151.6551	$1,151.65	$1,151.65	$1,151.60