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	$10.97	3.830%	$11.3902	$11.39	$11.40	$11.40
Purchase #2	$186.38	7.141%	$199.6894	$199.69	$199.70	$199.70
Purchase #3	$111.39	10.515%	$123.1027	$123.10	$123.10	$123.10
Purchase #4	$111.41	12.609%	$125.4577	$125.46	$125.45	$125.50
Purchase #5	$238.77	11.250%	$265.6316	$265.63	$265.65	$265.60
Purchase #6	$127.85	6.728%	$136.4517	$136.45	$136.45	$136.50
Purchase #7	$209.87	10.263%	$231.409	$231.41	$231.40	$231.40
7 purchase totals =	$996.64		$1,093.1323	$1,093.13	$1,093.15	$1,093.20