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	$135.56	13.547%	$153.9243	$153.92	$153.90	$153.90
Purchase #2	$90.27	11.590%	$100.7323	$100.73	$100.75	$100.70
Purchase #3	$193.72	6.305%	$205.934	$205.93	$205.95	$205.90
Purchase #4	$176.98	5.250%	$186.2715	$186.27	$186.25	$186.30
Purchase #5	$196.45	11.696%	$219.4268	$219.43	$219.45	$219.40
Purchase #6	$110.77	10.705%	$122.6279	$122.63	$122.65	$122.60
Purchase #7	$18.43	11.403%	$20.5316	$20.53	$20.55	$20.50
7 purchase totals =	$922.18		$1,009.4484	$1,009.44	$1,009.50	$1,009.30