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	$250.83	10.528%	$277.2374	$277.24	$277.25	$277.20
Purchase #2	$186.59	5.323%	$196.5222	$196.52	$196.50	$196.50
Purchase #3	$85.68	5.316%	$90.2347	$90.23	$90.25	$90.20
Purchase #4	$170.70	4.598%	$178.5488	$178.55	$178.55	$178.50
Purchase #5	$228.87	4.114%	$238.2857	$238.29	$238.30	$238.30
Purchase #6	$84.40	6.304%	$89.7206	$89.72	$89.70	$89.70
Purchase #7	$42.71	4.791%	$44.7562	$44.76	$44.75	$44.80
7 purchase totals =	$1,049.78		$1,115.3056	$1,115.31	$1,115.30	$1,115.20