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	$33.29	10.768%	$36.8747	$36.87	$36.85	$36.90
Purchase #2	$216.36	8.294%	$234.3049	$234.30	$234.30	$234.30
Purchase #3	$34.41	8.180%	$37.2247	$37.22	$37.20	$37.20
Purchase #4	$131.92	7.515%	$141.8338	$141.83	$141.85	$141.80
Purchase #5	$224.52	3.269%	$231.8596	$231.86	$231.85	$231.90
Purchase #6	$233.69	13.168%	$264.4623	$264.46	$264.45	$264.50
Purchase #7	$59.53	12.372%	$66.8951	$66.90	$66.90	$66.90
7 purchase totals =	$933.72		$1,013.4551	$1,013.44	$1,013.40	$1,013.50