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	$40.39	9.736%	$44.3224	$44.32	$44.30	$44.30
Purchase #2	$69.41	13.554%	$78.8178	$78.82	$78.80	$78.80
Purchase #3	$122.92	5.719%	$129.9498	$129.95	$129.95	$129.90
Purchase #4	$93.96	12.261%	$105.4804	$105.48	$105.50	$105.50
Purchase #5	$209.56	10.479%	$231.5198	$231.52	$231.50	$231.50
Purchase #6	$124.40	9.229%	$135.8809	$135.88	$135.90	$135.90
Purchase #7	$250.64	11.467%	$279.3809	$279.38	$279.40	$279.40
7 purchase totals =	$911.28		$1,005.3520	$1,005.35	$1,005.35	$1,005.30