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	$229.40	13.273%	$259.8483	$259.85	$259.85	$259.80
Purchase #2	$233.64	8.673%	$253.9036	$253.90	$253.90	$253.90
Purchase #3	$42.36	3.369%	$43.7871	$43.79	$43.80	$43.80
Purchase #4	$223.44	13.154%	$252.8313	$252.83	$252.85	$252.80
Purchase #5	$162.38	12.632%	$182.8918	$182.89	$182.90	$182.90
Purchase #6	$130.70	4.739%	$136.8939	$136.89	$136.90	$136.90
Purchase #7	$14.28	10.245%	$15.743	$15.74	$15.75	$15.70
7 purchase totals =	$1,036.20		$1,145.8990	$1,145.89	$1,145.95	$1,145.80