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	$138.69	9.791%	$152.2691	$152.27	$152.25	$152.30
Purchase #2	$101.37	6.524%	$107.9834	$107.98	$108.00	$108.00
Purchase #3	$103.31	5.792%	$109.2937	$109.29	$109.30	$109.30
Purchase #4	$205.80	10.873%	$228.1766	$228.18	$228.20	$228.20
Purchase #5	$135.64	5.844%	$143.5668	$143.57	$143.55	$143.60
Purchase #6	$179.57	9.287%	$196.2467	$196.25	$196.25	$196.20
Purchase #7	$97.71	12.750%	$110.168	$110.17	$110.15	$110.20
7 purchase totals =	$962.09		$1,047.7043	$1,047.71	$1,047.70	$1,047.80