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	$240.46	9.354%	$262.9526	$262.95	$262.95	$263.00
Purchase #2	$145.81	11.336%	$162.339	$162.34	$162.35	$162.30
Purchase #3	$9.92	3.465%	$10.2637	$10.26	$10.25	$10.30
Purchase #4	$120.32	3.853%	$124.9559	$124.96	$124.95	$125.00
Purchase #5	$227.69	12.580%	$256.3334	$256.33	$256.35	$256.30
Purchase #6	$123.94	10.174%	$136.5497	$136.55	$136.55	$136.50
Purchase #7	$81.41	10.589%	$90.0305	$90.03	$90.05	$90.00
7 purchase totals =	$949.55		$1,043.4248	$1,043.42	$1,043.45	$1,043.40